diff --git a/app/api/api_v1/api.py b/app/api/api_v1/api.py
new file mode 100644
index 0000000..8d16179
--- /dev/null
+++ b/app/api/api_v1/api.py
@@ -0,0 +1,12 @@
+from fastapi import APIRouter
+
+from app.api.api_v1.endpoints import auth, users, products, categories, suppliers, inventory, orders
+
+api_router = APIRouter()
+api_router.include_router(auth.router, prefix="/auth", tags=["Authentication"])
+api_router.include_router(users.router, prefix="/users", tags=["Users"])
+api_router.include_router(products.router, prefix="/products", tags=["Products"])
+api_router.include_router(categories.router, prefix="/categories", tags=["Categories"])
+api_router.include_router(suppliers.router, prefix="/suppliers", tags=["Suppliers"])
+api_router.include_router(inventory.router, prefix="/inventory", tags=["Inventory"])
+api_router.include_router(orders.router, prefix="/orders", tags=["Orders"])
\ No newline at end of file
diff --git a/app/api/api_v1/endpoints/auth.py b/app/api/api_v1/endpoints/auth.py
new file mode 100644
index 0000000..a8e3782
--- /dev/null
+++ b/app/api/api_v1/endpoints/auth.py
@@ -0,0 +1,55 @@
+from datetime import timedelta
+from typing import Any
+
+from fastapi import APIRouter, Depends, HTTPException
+from fastapi.security import OAuth2PasswordRequestForm
+from sqlalchemy.orm import Session
+
+from app import crud, schemas
+from app.api import deps
+from app.core import security
+from app.core.config import settings
+
+router = APIRouter()
+
+
+@router.post("/login/access-token", response_model=schemas.Token)
+def login_access_token(
+    db: Session = Depends(deps.get_db), form_data: OAuth2PasswordRequestForm = Depends()
+) -> Any:
+    """
+    OAuth2 compatible token login, get an access token for future requests
+    """
+    user = crud.user.authenticate(
+        db, email=form_data.username, password=form_data.password
+    )
+    if not user:
+        raise HTTPException(status_code=400, detail="Incorrect email or password")
+    elif not crud.user.is_active(user):
+        raise HTTPException(status_code=400, detail="Inactive user")
+    access_token_expires = timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
+    return {
+        "access_token": security.create_access_token(
+            user.id, expires_delta=access_token_expires
+        ),
+        "token_type": "bearer",
+    }
+
+
+@router.post("/register", response_model=schemas.User)
+def register_new_user(
+    *,
+    db: Session = Depends(deps.get_db),
+    user_in: schemas.UserCreate,
+) -> Any:
+    """
+    Create new user.
+    """
+    user = crud.user.get_by_email(db, email=user_in.email)
+    if user:
+        raise HTTPException(
+            status_code=400,
+            detail="The user with this email already exists in the system.",
+        )
+    user = crud.user.create(db, obj_in=user_in)
+    return user
\ No newline at end of file
diff --git a/app/api/api_v1/endpoints/categories.py b/app/api/api_v1/endpoints/categories.py
new file mode 100644
index 0000000..0e55e59
--- /dev/null
+++ b/app/api/api_v1/endpoints/categories.py
@@ -0,0 +1,94 @@
+from typing import Any, List
+
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[schemas.Category])
+def read_categories(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve categories.
+    """
+    categories = crud.category.get_multi(db, skip=skip, limit=limit)
+    return categories
+
+
+@router.post("/", response_model=schemas.Category)
+def create_category(
+    *,
+    db: Session = Depends(deps.get_db),
+    category_in: schemas.CategoryCreate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Create new category.
+    """
+    category = crud.category.get_by_name(db, name=category_in.name)
+    if category:
+        raise HTTPException(
+            status_code=400,
+            detail="The category with this name already exists in the system.",
+        )
+    category = crud.category.create(db, obj_in=category_in)
+    return category
+
+
+@router.put("/{id}", response_model=schemas.Category)
+def update_category(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    category_in: schemas.CategoryUpdate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update a category.
+    """
+    category = crud.category.get(db, id=id)
+    if not category:
+        raise HTTPException(status_code=404, detail="Category not found")
+    category = crud.category.update(db, db_obj=category, obj_in=category_in)
+    return category
+
+
+@router.get("/{id}", response_model=schemas.Category)
+def read_category(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get category by ID.
+    """
+    category = crud.category.get(db, id=id)
+    if not category:
+        raise HTTPException(status_code=404, detail="Category not found")
+    return category
+
+
+@router.delete("/{id}", response_model=schemas.Category)
+def delete_category(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Delete a category.
+    """
+    category = crud.category.get(db, id=id)
+    if not category:
+        raise HTTPException(status_code=404, detail="Category not found")
+    category = crud.category.remove(db, id=id)
+    return category
\ No newline at end of file
diff --git a/app/api/api_v1/endpoints/inventory.py b/app/api/api_v1/endpoints/inventory.py
new file mode 100644
index 0000000..200a200
--- /dev/null
+++ b/app/api/api_v1/endpoints/inventory.py
@@ -0,0 +1,155 @@
+from typing import Any, List
+
+from fastapi import APIRouter, Depends, HTTPException, Body
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[schemas.InventoryItem])
+def read_inventory_items(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve inventory items.
+    """
+    inventory_items = crud.inventory.get_multi(db, skip=skip, limit=limit)
+    return inventory_items
+
+
+@router.get("/low-stock", response_model=List[schemas.InventoryItem])
+def read_low_stock_items(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve low stock inventory items.
+    """
+    inventory_items = crud.inventory.get_low_stock(db, skip=skip, limit=limit)
+    return inventory_items
+
+
+@router.post("/", response_model=schemas.InventoryItem)
+def create_inventory_item(
+    *,
+    db: Session = Depends(deps.get_db),
+    item_in: schemas.InventoryItemCreate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Create new inventory item.
+    """
+    product = crud.product.get(db, id=item_in.product_id)
+    if not product:
+        raise HTTPException(status_code=404, detail="Product not found")
+    
+    existing_item = crud.inventory.get_by_product(db, product_id=item_in.product_id)
+    if existing_item:
+        raise HTTPException(
+            status_code=400,
+            detail="An inventory item for this product already exists.",
+        )
+        
+    inventory_item = crud.inventory.create(db, obj_in=item_in)
+    return inventory_item
+
+
+@router.put("/{id}", response_model=schemas.InventoryItem)
+def update_inventory_item(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    item_in: schemas.InventoryItemUpdate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update an inventory item.
+    """
+    inventory_item = crud.inventory.get(db, id=id)
+    if not inventory_item:
+        raise HTTPException(status_code=404, detail="Inventory item not found")
+    
+    inventory_item = crud.inventory.update(db, db_obj=inventory_item, obj_in=item_in)
+    return inventory_item
+
+
+@router.put("/{id}/adjust-quantity", response_model=schemas.InventoryItem)
+def adjust_inventory_quantity(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    quantity_change: int = Body(..., embed=True),
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Adjust inventory quantity. Use positive number to increase, negative to decrease.
+    """
+    inventory_item = crud.inventory.get(db, id=id)
+    if not inventory_item:
+        raise HTTPException(status_code=404, detail="Inventory item not found")
+    
+    if inventory_item.quantity + quantity_change < 0:
+        raise HTTPException(
+            status_code=400,
+            detail="Cannot reduce quantity below zero."
+        )
+    
+    inventory_item = crud.inventory.update_quantity(db, item_id=id, quantity_change=quantity_change)
+    return inventory_item
+
+
+@router.get("/{id}", response_model=schemas.InventoryItem)
+def read_inventory_item(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get inventory item by ID.
+    """
+    inventory_item = crud.inventory.get(db, id=id)
+    if not inventory_item:
+        raise HTTPException(status_code=404, detail="Inventory item not found")
+    return inventory_item
+
+
+@router.get("/product/{product_id}", response_model=schemas.InventoryItem)
+def read_inventory_by_product(
+    *,
+    db: Session = Depends(deps.get_db),
+    product_id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get inventory item by product ID.
+    """
+    inventory_item = crud.inventory.get_by_product(db, product_id=product_id)
+    if not inventory_item:
+        raise HTTPException(status_code=404, detail="Inventory item not found")
+    return inventory_item
+
+
+@router.delete("/{id}", response_model=schemas.InventoryItem)
+def delete_inventory_item(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Delete an inventory item.
+    """
+    inventory_item = crud.inventory.get(db, id=id)
+    if not inventory_item:
+        raise HTTPException(status_code=404, detail="Inventory item not found")
+    inventory_item = crud.inventory.remove(db, id=id)
+    return inventory_item
\ No newline at end of file
diff --git a/app/api/api_v1/endpoints/orders.py b/app/api/api_v1/endpoints/orders.py
new file mode 100644
index 0000000..f118678
--- /dev/null
+++ b/app/api/api_v1/endpoints/orders.py
@@ -0,0 +1,134 @@
+from typing import Any, List
+
+from fastapi import APIRouter, Depends, HTTPException, Body
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+from app.models.order import OrderStatus
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[schemas.Order])
+def read_orders(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    status: OrderStatus = None,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve orders.
+    """
+    if crud.user.is_superuser(current_user):
+        if status:
+            orders = crud.order.get_by_status(db, status=status, skip=skip, limit=limit)
+        else:
+            orders = crud.order.get_multi(db, skip=skip, limit=limit)
+    else:
+        orders = crud.order.get_by_user(db, user_id=current_user.id, skip=skip, limit=limit)
+        if status:
+            orders = [order for order in orders if order.status == status]
+    return orders
+
+
+@router.post("/", response_model=schemas.Order)
+def create_order(
+    *,
+    db: Session = Depends(deps.get_db),
+    order_in: schemas.OrderCreate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Create new order.
+    """
+    # Verify all products exist
+    for item in order_in.order_items:
+        product = crud.product.get(db, id=item.product_id)
+        if not product:
+            raise HTTPException(
+                status_code=404,
+                detail=f"Product with id {item.product_id} not found"
+            )
+            
+        # Check if there's enough inventory
+        inventory = crud.inventory.get_by_product(db, product_id=item.product_id)
+        if inventory and inventory.quantity < item.quantity:
+            raise HTTPException(
+                status_code=400,
+                detail=f"Not enough stock for product {product.name}. Available: {inventory.quantity}"
+            )
+    
+    # Create order
+    order = crud.order.create(db, obj_in=order_in, user_id=current_user.id)
+    
+    # Update inventory
+    for item in order_in.order_items:
+        inventory = crud.inventory.get_by_product(db, product_id=item.product_id)
+        if inventory:
+            crud.inventory.update_quantity(db, item_id=inventory.id, quantity_change=-item.quantity)
+    
+    return order
+
+
+@router.put("/{id}/status", response_model=schemas.Order)
+def update_order_status(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    status: OrderStatus = Body(..., embed=True),
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update order status.
+    """
+    order = crud.order.get(db, id=id)
+    if not order:
+        raise HTTPException(status_code=404, detail="Order not found")
+    
+    # Only superusers can update orders they don't own
+    if order.user_id != current_user.id and not crud.user.is_superuser(current_user):
+        raise HTTPException(status_code=403, detail="Not enough permissions")
+        
+    order_in = schemas.OrderUpdate(status=status)
+    order = crud.order.update(db, db_obj=order, obj_in=order_in)
+    return order
+
+
+@router.get("/{id}", response_model=schemas.Order)
+def read_order(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get order by ID.
+    """
+    order = crud.order.get(db, id=id)
+    if not order:
+        raise HTTPException(status_code=404, detail="Order not found")
+    
+    # Only superusers can view orders they don't own
+    if order.user_id != current_user.id and not crud.user.is_superuser(current_user):
+        raise HTTPException(status_code=403, detail="Not enough permissions")
+        
+    return order
+
+
+@router.delete("/{id}", response_model=schemas.Order)
+def delete_order(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Delete an order.
+    """
+    order = crud.order.get(db, id=id)
+    if not order:
+        raise HTTPException(status_code=404, detail="Order not found")
+    order = crud.order.remove(db, id=id)
+    return order
\ No newline at end of file
diff --git a/app/api/api_v1/endpoints/products.py b/app/api/api_v1/endpoints/products.py
new file mode 100644
index 0000000..6d4d087
--- /dev/null
+++ b/app/api/api_v1/endpoints/products.py
@@ -0,0 +1,136 @@
+from typing import Any, List, Optional
+
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[schemas.Product])
+def read_products(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    category_id: Optional[int] = None,
+    supplier_id: Optional[int] = None,
+    active_only: bool = False,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve products.
+    """
+    if category_id:
+        products = crud.product.get_by_category(db, category_id=category_id, skip=skip, limit=limit)
+    elif supplier_id:
+        products = crud.product.get_by_supplier(db, supplier_id=supplier_id, skip=skip, limit=limit)
+    elif active_only:
+        products = crud.product.get_active(db, skip=skip, limit=limit)
+    else:
+        products = crud.product.get_multi(db, skip=skip, limit=limit)
+    return products
+
+
+@router.post("/", response_model=schemas.Product)
+def create_product(
+    *,
+    db: Session = Depends(deps.get_db),
+    product_in: schemas.ProductCreate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Create new product.
+    """
+    product = crud.product.get_by_sku(db, sku=product_in.sku)
+    if product:
+        raise HTTPException(
+            status_code=400,
+            detail="The product with this SKU already exists in the system.",
+        )
+    product = crud.product.create(db, obj_in=product_in)
+    return product
+
+
+@router.put("/{id}", response_model=schemas.Product)
+def update_product(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    product_in: schemas.ProductUpdate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update a product.
+    """
+    product = crud.product.get(db, id=id)
+    if not product:
+        raise HTTPException(status_code=404, detail="Product not found")
+    product = crud.product.update(db, db_obj=product, obj_in=product_in)
+    return product
+
+
+@router.get("/{id}", response_model=schemas.Product)
+def read_product(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get product by ID.
+    """
+    product = crud.product.get(db, id=id)
+    if not product:
+        raise HTTPException(status_code=404, detail="Product not found")
+    return product
+
+
+@router.get("/sku/{sku}", response_model=schemas.Product)
+def read_product_by_sku(
+    *,
+    db: Session = Depends(deps.get_db),
+    sku: str,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get product by SKU.
+    """
+    product = crud.product.get_by_sku(db, sku=sku)
+    if not product:
+        raise HTTPException(status_code=404, detail="Product not found")
+    return product
+
+
+@router.get("/barcode/{barcode}", response_model=schemas.Product)
+def read_product_by_barcode(
+    *,
+    db: Session = Depends(deps.get_db),
+    barcode: str,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get product by barcode.
+    """
+    product = crud.product.get_by_barcode(db, barcode=barcode)
+    if not product:
+        raise HTTPException(status_code=404, detail="Product not found")
+    return product
+
+
+@router.delete("/{id}", response_model=schemas.Product)
+def delete_product(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Delete a product.
+    """
+    product = crud.product.get(db, id=id)
+    if not product:
+        raise HTTPException(status_code=404, detail="Product not found")
+    product = crud.product.remove(db, id=id)
+    return product
\ No newline at end of file
diff --git a/app/api/api_v1/endpoints/suppliers.py b/app/api/api_v1/endpoints/suppliers.py
new file mode 100644
index 0000000..c1143ad
--- /dev/null
+++ b/app/api/api_v1/endpoints/suppliers.py
@@ -0,0 +1,94 @@
+from typing import Any, List
+
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[schemas.Supplier])
+def read_suppliers(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve suppliers.
+    """
+    suppliers = crud.supplier.get_multi(db, skip=skip, limit=limit)
+    return suppliers
+
+
+@router.post("/", response_model=schemas.Supplier)
+def create_supplier(
+    *,
+    db: Session = Depends(deps.get_db),
+    supplier_in: schemas.SupplierCreate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Create new supplier.
+    """
+    supplier = crud.supplier.get_by_name(db, name=supplier_in.name)
+    if supplier:
+        raise HTTPException(
+            status_code=400,
+            detail="The supplier with this name already exists in the system.",
+        )
+    supplier = crud.supplier.create(db, obj_in=supplier_in)
+    return supplier
+
+
+@router.put("/{id}", response_model=schemas.Supplier)
+def update_supplier(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    supplier_in: schemas.SupplierUpdate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update a supplier.
+    """
+    supplier = crud.supplier.get(db, id=id)
+    if not supplier:
+        raise HTTPException(status_code=404, detail="Supplier not found")
+    supplier = crud.supplier.update(db, db_obj=supplier, obj_in=supplier_in)
+    return supplier
+
+
+@router.get("/{id}", response_model=schemas.Supplier)
+def read_supplier(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get supplier by ID.
+    """
+    supplier = crud.supplier.get(db, id=id)
+    if not supplier:
+        raise HTTPException(status_code=404, detail="Supplier not found")
+    return supplier
+
+
+@router.delete("/{id}", response_model=schemas.Supplier)
+def delete_supplier(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Delete a supplier.
+    """
+    supplier = crud.supplier.get(db, id=id)
+    if not supplier:
+        raise HTTPException(status_code=404, detail="Supplier not found")
+    supplier = crud.supplier.remove(db, id=id)
+    return supplier
\ No newline at end of file
diff --git a/app/api/api_v1/endpoints/users.py b/app/api/api_v1/endpoints/users.py
new file mode 100644
index 0000000..82e3955
--- /dev/null
+++ b/app/api/api_v1/endpoints/users.py
@@ -0,0 +1,100 @@
+from typing import Any, List
+
+from fastapi import APIRouter, Body, Depends, HTTPException
+from fastapi.encoders import jsonable_encoder
+from pydantic import EmailStr
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[schemas.User])
+def read_users(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: models.User = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Retrieve users.
+    """
+    users = crud.user.get_multi(db, skip=skip, limit=limit)
+    return users
+
+
+@router.get("/me", response_model=schemas.User)
+def read_user_me(
+    db: Session = Depends(deps.get_db),
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get current user.
+    """
+    return current_user
+
+
+@router.get("/{user_id}", response_model=schemas.User)
+def read_user_by_id(
+    user_id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+    db: Session = Depends(deps.get_db),
+) -> Any:
+    """
+    Get a specific user by id.
+    """
+    user = crud.user.get(db, id=user_id)
+    if user == current_user:
+        return user
+    if not crud.user.is_superuser(current_user):
+        raise HTTPException(
+            status_code=400, detail="The user doesn't have enough privileges"
+        )
+    return user
+
+
+@router.put("/me", response_model=schemas.User)
+def update_user_me(
+    *,
+    db: Session = Depends(deps.get_db),
+    full_name: str = Body(None),
+    email: EmailStr = Body(None),
+    password: str = Body(None),
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update own user.
+    """
+    current_user_data = jsonable_encoder(current_user)
+    user_in = schemas.UserUpdate(**current_user_data)
+    if full_name is not None:
+        user_in.full_name = full_name
+    if email is not None:
+        user_in.email = email
+    if password is not None:
+        user_in.password = password
+    user = crud.user.update(db, db_obj=current_user, obj_in=user_in)
+    return user
+
+
+@router.put("/{user_id}", response_model=schemas.User)
+def update_user(
+    *,
+    db: Session = Depends(deps.get_db),
+    user_id: int,
+    user_in: schemas.UserUpdate,
+    current_user: models.User = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Update a user.
+    """
+    user = crud.user.get(db, id=user_id)
+    if not user:
+        raise HTTPException(
+            status_code=404,
+            detail="The user with this id does not exist in the system",
+        )
+    user = crud.user.update(db, db_obj=user, obj_in=user_in)
+    return user
\ No newline at end of file
diff --git a/app/api/deps.py b/app/api/deps.py
new file mode 100644
index 0000000..37c05d9
--- /dev/null
+++ b/app/api/deps.py
@@ -0,0 +1,52 @@
+
+from fastapi import Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordBearer
+from jose import jwt
+from pydantic import ValidationError
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.core import security
+from app.core.config import settings
+from app.db.session import get_db
+
+oauth2_scheme = OAuth2PasswordBearer(
+    tokenUrl=f"{settings.API_V1_STR}/auth/login"
+)
+
+
+def get_current_user(
+    db: Session = Depends(get_db), token: str = Depends(oauth2_scheme)
+) -> models.User:
+    try:
+        payload = jwt.decode(
+            token, settings.SECRET_KEY, algorithms=[security.ALGORITHM]
+        )
+        token_data = schemas.TokenPayload(**payload)
+    except (jwt.JWTError, ValidationError):
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Could not validate credentials",
+        )
+    user = crud.user.get(db, id=token_data.sub)
+    if not user:
+        raise HTTPException(status_code=404, detail="User not found")
+    return user
+
+
+def get_current_active_user(
+    current_user: models.User = Depends(get_current_user),
+) -> models.User:
+    if not current_user.is_active:
+        raise HTTPException(status_code=400, detail="Inactive user")
+    return current_user
+
+
+def get_current_active_superuser(
+    current_user: models.User = Depends(get_current_user),
+) -> models.User:
+    if not current_user.is_superuser:
+        raise HTTPException(
+            status_code=400, detail="The user doesn't have enough privileges"
+        )
+    return current_user
\ No newline at end of file
diff --git a/app/core/config.py b/app/core/config.py
new file mode 100644
index 0000000..09950d7
--- /dev/null
+++ b/app/core/config.py
@@ -0,0 +1,43 @@
+import os
+from pathlib import Path
+from typing import List, Union
+
+from pydantic import AnyHttpUrl, BaseSettings, EmailStr, validator
+
+
+class Settings(BaseSettings):
+    API_V1_STR: str = "/api/v1"
+    SECRET_KEY: str = os.getenv("SECRET_KEY", "your-secret-key-for-development-only")
+    ACCESS_TOKEN_EXPIRE_MINUTES: int = 60 * 24 * 8  # 8 days
+    
+    # Server settings
+    SERVER_NAME: str = os.getenv("SERVER_NAME", "Small Business Inventory")
+    SERVER_HOST: AnyHttpUrl = os.getenv("SERVER_HOST", "http://localhost")
+    PROJECT_NAME: str = "Small Business Inventory Management System"
+    
+    # Database settings
+    DB_DIR = Path("/app") / "storage" / "db"
+    DB_DIR.mkdir(parents=True, exist_ok=True)
+    SQLALCHEMY_DATABASE_URL: str = f"sqlite:///{DB_DIR}/db.sqlite"
+    
+    # CORS settings
+    BACKEND_CORS_ORIGINS: List[AnyHttpUrl] = []
+
+    @validator("BACKEND_CORS_ORIGINS", pre=True)
+    def assemble_cors_origins(cls, v: Union[str, List[str]]) -> Union[List[str], str]:
+        if isinstance(v, str) and not v.startswith("["):
+            return [i.strip() for i in v.split(",")]
+        elif isinstance(v, (list, str)):
+            return v
+        raise ValueError(v)
+    
+    # Superuser settings
+    FIRST_SUPERUSER: EmailStr = os.getenv("FIRST_SUPERUSER", "admin@example.com")
+    FIRST_SUPERUSER_PASSWORD: str = os.getenv("FIRST_SUPERUSER_PASSWORD", "admin")
+
+    class Config:
+        case_sensitive = True
+        env_file = ".env"
+
+
+settings = Settings()
\ No newline at end of file
diff --git a/app/core/security.py b/app/core/security.py
new file mode 100644
index 0000000..c9c4d3f
--- /dev/null
+++ b/app/core/security.py
@@ -0,0 +1,33 @@
+from datetime import datetime, timedelta
+from typing import Any, Union
+
+from jose import jwt
+from passlib.context import CryptContext
+
+from app.core.config import settings
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+
+ALGORITHM = "HS256"
+
+
+def create_access_token(
+    subject: Union[str, Any], expires_delta: timedelta = None
+) -> str:
+    if expires_delta:
+        expire = datetime.utcnow() + expires_delta
+    else:
+        expire = datetime.utcnow() + timedelta(
+            minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES
+        )
+    to_encode = {"exp": expire, "sub": str(subject)}
+    encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=ALGORITHM)
+    return encoded_jwt
+
+
+def verify_password(plain_password: str, hashed_password: str) -> bool:
+    return pwd_context.verify(plain_password, hashed_password)
+
+
+def get_password_hash(password: str) -> str:
+    return pwd_context.hash(password)
\ No newline at end of file
diff --git a/app/crud/__init__.py b/app/crud/__init__.py
new file mode 100644
index 0000000..515c943
--- /dev/null
+++ b/app/crud/__init__.py
@@ -0,0 +1,6 @@
+from .crud_user import user
+from .crud_product import product
+from .crud_category import category
+from .crud_supplier import supplier
+from .crud_inventory import inventory
+from .crud_order import order
\ No newline at end of file
diff --git a/app/crud/base.py b/app/crud/base.py
new file mode 100644
index 0000000..43040ef
--- /dev/null
+++ b/app/crud/base.py
@@ -0,0 +1,66 @@
+from typing import Any, Dict, Generic, List, Optional, Type, TypeVar, Union
+
+from fastapi.encoders import jsonable_encoder
+from pydantic import BaseModel
+from sqlalchemy.orm import Session
+
+from app.db.base_class import Base
+
+ModelType = TypeVar("ModelType", bound=Base)
+CreateSchemaType = TypeVar("CreateSchemaType", bound=BaseModel)
+UpdateSchemaType = TypeVar("UpdateSchemaType", bound=BaseModel)
+
+
+class CRUDBase(Generic[ModelType, CreateSchemaType, UpdateSchemaType]):
+    def __init__(self, model: Type[ModelType]):
+        """
+        CRUD object with default methods to Create, Read, Update, Delete (CRUD).
+
+        **Parameters**
+
+        * `model`: A SQLAlchemy model class
+        * `schema`: A Pydantic model (schema) class
+        """
+        self.model = model
+
+    def get(self, db: Session, id: Any) -> Optional[ModelType]:
+        return db.query(self.model).filter(self.model.id == id).first()
+
+    def get_multi(
+        self, db: Session, *, skip: int = 0, limit: int = 100
+    ) -> List[ModelType]:
+        return db.query(self.model).offset(skip).limit(limit).all()
+
+    def create(self, db: Session, *, obj_in: CreateSchemaType) -> ModelType:
+        obj_in_data = jsonable_encoder(obj_in)
+        db_obj = self.model(**obj_in_data)
+        db.add(db_obj)
+        db.commit()
+        db.refresh(db_obj)
+        return db_obj
+
+    def update(
+        self,
+        db: Session,
+        *,
+        db_obj: ModelType,
+        obj_in: Union[UpdateSchemaType, Dict[str, Any]]
+    ) -> ModelType:
+        obj_data = jsonable_encoder(db_obj)
+        if isinstance(obj_in, dict):
+            update_data = obj_in
+        else:
+            update_data = obj_in.dict(exclude_unset=True)
+        for field in obj_data:
+            if field in update_data:
+                setattr(db_obj, field, update_data[field])
+        db.add(db_obj)
+        db.commit()
+        db.refresh(db_obj)
+        return db_obj
+
+    def remove(self, db: Session, *, id: int) -> ModelType:
+        obj = db.query(self.model).get(id)
+        db.delete(obj)
+        db.commit()
+        return obj
\ No newline at end of file
diff --git a/app/crud/crud_category.py b/app/crud/crud_category.py
new file mode 100644
index 0000000..3593a96
--- /dev/null
+++ b/app/crud/crud_category.py
@@ -0,0 +1,20 @@
+from typing import List
+
+from sqlalchemy.orm import Session
+
+from app.crud.base import CRUDBase
+from app.models.category import Category
+from app.schemas.category import CategoryCreate, CategoryUpdate
+
+
+class CRUDCategory(CRUDBase[Category, CategoryCreate, CategoryUpdate]):
+    def get_by_name(self, db: Session, *, name: str) -> Category:
+        return db.query(Category).filter(Category.name == name).first()
+    
+    def get_multi_by_ids(
+        self, db: Session, *, ids: List[int], skip: int = 0, limit: int = 100
+    ) -> List[Category]:
+        return db.query(Category).filter(Category.id.in_(ids)).offset(skip).limit(limit).all()
+
+
+category = CRUDCategory(Category)
\ No newline at end of file
diff --git a/app/crud/crud_inventory.py b/app/crud/crud_inventory.py
new file mode 100644
index 0000000..889c3bc
--- /dev/null
+++ b/app/crud/crud_inventory.py
@@ -0,0 +1,41 @@
+from typing import List, Optional
+
+from sqlalchemy.orm import Session
+
+from app.crud.base import CRUDBase
+from app.models.inventory import InventoryItem
+from app.schemas.inventory import InventoryItemCreate, InventoryItemUpdate
+
+
+class CRUDInventory(CRUDBase[InventoryItem, InventoryItemCreate, InventoryItemUpdate]):
+    def get_by_product(
+        self, db: Session, *, product_id: int
+    ) -> Optional[InventoryItem]:
+        return db.query(InventoryItem).filter(InventoryItem.product_id == product_id).first()
+    
+    def get_low_stock(
+        self, db: Session, *, skip: int = 0, limit: int = 100
+    ) -> List[InventoryItem]:
+        return (
+            db.query(InventoryItem)
+            .filter(InventoryItem.quantity <= InventoryItem.min_stock_level)
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+    
+    def update_quantity(
+        self, db: Session, *, item_id: int, quantity_change: int
+    ) -> InventoryItem:
+        db_obj = db.query(InventoryItem).filter(InventoryItem.id == item_id).first()
+        if db_obj:
+            new_quantity = db_obj.quantity + quantity_change
+            # Ensure quantity never goes below 0
+            db_obj.quantity = max(0, new_quantity)
+            db.add(db_obj)
+            db.commit()
+            db.refresh(db_obj)
+        return db_obj
+
+
+inventory = CRUDInventory(InventoryItem)
\ No newline at end of file
diff --git a/app/crud/crud_order.py b/app/crud/crud_order.py
new file mode 100644
index 0000000..87d337e
--- /dev/null
+++ b/app/crud/crud_order.py
@@ -0,0 +1,47 @@
+from typing import List
+
+from sqlalchemy.orm import Session
+
+from app.crud.base import CRUDBase
+from app.models.order import Order, OrderItem
+from app.schemas.order import OrderCreate, OrderUpdate
+
+
+class CRUDOrder(CRUDBase[Order, OrderCreate, OrderUpdate]):
+    def create(self, db: Session, *, obj_in: OrderCreate, user_id: int) -> Order:
+        # Calculate total amount from order items
+        total_amount = sum(item.unit_price * item.quantity for item in obj_in.order_items)
+        
+        # Create order
+        order_data = obj_in.dict(exclude={"order_items"})
+        db_obj = Order(**order_data, user_id=user_id, total_amount=total_amount)
+        db.add(db_obj)
+        db.commit()
+        db.refresh(db_obj)
+        
+        # Create order items
+        for item in obj_in.order_items:
+            db_item = OrderItem(
+                order_id=db_obj.id,
+                product_id=item.product_id,
+                quantity=item.quantity,
+                unit_price=item.unit_price
+            )
+            db.add(db_item)
+        
+        db.commit()
+        db.refresh(db_obj)
+        return db_obj
+    
+    def get_by_user(
+        self, db: Session, *, user_id: int, skip: int = 0, limit: int = 100
+    ) -> List[Order]:
+        return db.query(Order).filter(Order.user_id == user_id).offset(skip).limit(limit).all()
+    
+    def get_by_status(
+        self, db: Session, *, status: str, skip: int = 0, limit: int = 100
+    ) -> List[Order]:
+        return db.query(Order).filter(Order.status == status).offset(skip).limit(limit).all()
+
+
+order = CRUDOrder(Order)
\ No newline at end of file
diff --git a/app/crud/crud_product.py b/app/crud/crud_product.py
new file mode 100644
index 0000000..8aa9b90
--- /dev/null
+++ b/app/crud/crud_product.py
@@ -0,0 +1,33 @@
+from typing import List, Optional
+
+from sqlalchemy.orm import Session
+
+from app.crud.base import CRUDBase
+from app.models.product import Product
+from app.schemas.product import ProductCreate, ProductUpdate
+
+
+class CRUDProduct(CRUDBase[Product, ProductCreate, ProductUpdate]):
+    def get_by_sku(self, db: Session, *, sku: str) -> Optional[Product]:
+        return db.query(Product).filter(Product.sku == sku).first()
+    
+    def get_by_barcode(self, db: Session, *, barcode: str) -> Optional[Product]:
+        return db.query(Product).filter(Product.barcode == barcode).first()
+    
+    def get_by_category(
+        self, db: Session, *, category_id: int, skip: int = 0, limit: int = 100
+    ) -> List[Product]:
+        return db.query(Product).filter(Product.category_id == category_id).offset(skip).limit(limit).all()
+    
+    def get_by_supplier(
+        self, db: Session, *, supplier_id: int, skip: int = 0, limit: int = 100
+    ) -> List[Product]:
+        return db.query(Product).filter(Product.supplier_id == supplier_id).offset(skip).limit(limit).all()
+    
+    def get_active(
+        self, db: Session, *, skip: int = 0, limit: int = 100
+    ) -> List[Product]:
+        return db.query(Product).filter(Product.is_active == True).offset(skip).limit(limit).all()
+
+
+product = CRUDProduct(Product)
\ No newline at end of file
diff --git a/app/crud/crud_supplier.py b/app/crud/crud_supplier.py
new file mode 100644
index 0000000..0ee47cc
--- /dev/null
+++ b/app/crud/crud_supplier.py
@@ -0,0 +1,20 @@
+from typing import List
+
+from sqlalchemy.orm import Session
+
+from app.crud.base import CRUDBase
+from app.models.supplier import Supplier
+from app.schemas.supplier import SupplierCreate, SupplierUpdate
+
+
+class CRUDSupplier(CRUDBase[Supplier, SupplierCreate, SupplierUpdate]):
+    def get_by_name(self, db: Session, *, name: str) -> Supplier:
+        return db.query(Supplier).filter(Supplier.name == name).first()
+    
+    def get_multi_by_ids(
+        self, db: Session, *, ids: List[int], skip: int = 0, limit: int = 100
+    ) -> List[Supplier]:
+        return db.query(Supplier).filter(Supplier.id.in_(ids)).offset(skip).limit(limit).all()
+
+
+supplier = CRUDSupplier(Supplier)
\ No newline at end of file
diff --git a/app/crud/crud_user.py b/app/crud/crud_user.py
new file mode 100644
index 0000000..6d16538
--- /dev/null
+++ b/app/crud/crud_user.py
@@ -0,0 +1,56 @@
+from typing import Any, Dict, Optional, Union
+
+from sqlalchemy.orm import Session
+
+from app.core.security import get_password_hash, verify_password
+from app.crud.base import CRUDBase
+from app.models.user import User
+from app.schemas.user import UserCreate, UserUpdate
+
+
+class CRUDUser(CRUDBase[User, UserCreate, UserUpdate]):
+    def get_by_email(self, db: Session, *, email: str) -> Optional[User]:
+        return db.query(User).filter(User.email == email).first()
+
+    def create(self, db: Session, *, obj_in: UserCreate) -> User:
+        db_obj = User(
+            email=obj_in.email,
+            hashed_password=get_password_hash(obj_in.password),
+            full_name=obj_in.full_name,
+            is_superuser=obj_in.is_superuser,
+            is_active=obj_in.is_active
+        )
+        db.add(db_obj)
+        db.commit()
+        db.refresh(db_obj)
+        return db_obj
+
+    def update(
+        self, db: Session, *, db_obj: User, obj_in: Union[UserUpdate, Dict[str, Any]]
+    ) -> User:
+        if isinstance(obj_in, dict):
+            update_data = obj_in
+        else:
+            update_data = obj_in.dict(exclude_unset=True)
+        if update_data.get("password"):
+            hashed_password = get_password_hash(update_data["password"])
+            del update_data["password"]
+            update_data["hashed_password"] = hashed_password
+        return super().update(db, db_obj=db_obj, obj_in=update_data)
+
+    def authenticate(self, db: Session, *, email: str, password: str) -> Optional[User]:
+        user = self.get_by_email(db, email=email)
+        if not user:
+            return None
+        if not verify_password(password, user.hashed_password):
+            return None
+        return user
+
+    def is_active(self, user: User) -> bool:
+        return user.is_active
+
+    def is_superuser(self, user: User) -> bool:
+        return user.is_superuser
+
+
+user = CRUDUser(User)
\ No newline at end of file
diff --git a/app/db/base.py b/app/db/base.py
new file mode 100644
index 0000000..6e01d4c
--- /dev/null
+++ b/app/db/base.py
@@ -0,0 +1,9 @@
+# Import all the models, so that Base has them before being
+# imported by Alembic
+from app.db.base_class import Base  # noqa
+from app.models.user import User  # noqa
+from app.models.product import Product  # noqa
+from app.models.category import Category  # noqa
+from app.models.supplier import Supplier  # noqa
+from app.models.inventory import InventoryItem  # noqa
+from app.models.order import Order, OrderItem  # noqa
\ No newline at end of file
diff --git a/app/db/base_class.py b/app/db/base_class.py
new file mode 100644
index 0000000..26f1478
--- /dev/null
+++ b/app/db/base_class.py
@@ -0,0 +1,14 @@
+from typing import Any
+
+from sqlalchemy.ext.declarative import as_declarative, declared_attr
+
+
+@as_declarative()
+class Base:
+    id: Any
+    __name__: str
+    
+    # Generate tablename automatically
+    @declared_attr
+    def __tablename__(cls) -> str:
+        return cls.__name__.lower()
\ No newline at end of file
diff --git a/app/db/session.py b/app/db/session.py
new file mode 100644
index 0000000..24b55ec
--- /dev/null
+++ b/app/db/session.py
@@ -0,0 +1,18 @@
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+from app.core.config import settings
+
+engine = create_engine(
+    settings.SQLALCHEMY_DATABASE_URL,
+    connect_args={"check_same_thread": False}
+)
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+
+def get_db():
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
\ No newline at end of file
diff --git a/app/models/category.py b/app/models/category.py
new file mode 100644
index 0000000..4e1e17b
--- /dev/null
+++ b/app/models/category.py
@@ -0,0 +1,13 @@
+from sqlalchemy import Column, Integer, String
+from sqlalchemy.orm import relationship
+
+from app.db.base_class import Base
+
+
+class Category(Base):
+    id = Column(Integer, primary_key=True, index=True)
+    name = Column(String, index=True, nullable=False)
+    description = Column(String, nullable=True)
+
+    # Relationships
+    products = relationship("Product", back_populates="category")
\ No newline at end of file
diff --git a/app/models/inventory.py b/app/models/inventory.py
new file mode 100644
index 0000000..6c0cf1a
--- /dev/null
+++ b/app/models/inventory.py
@@ -0,0 +1,20 @@
+from sqlalchemy import Column, Integer, String, ForeignKey, DateTime
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+
+from app.db.base_class import Base
+
+
+class InventoryItem(Base):
+    id = Column(Integer, primary_key=True, index=True)
+    quantity = Column(Integer, default=0, nullable=False)
+    location = Column(String, nullable=True)
+    last_updated = Column(DateTime, default=func.now(), onupdate=func.now())
+    min_stock_level = Column(Integer, default=0)
+    max_stock_level = Column(Integer, default=0)
+    
+    # Foreign keys
+    product_id = Column(Integer, ForeignKey("product.id"), nullable=False)
+    
+    # Relationships
+    product = relationship("Product", back_populates="inventory_items")
\ No newline at end of file
diff --git a/app/models/order.py b/app/models/order.py
new file mode 100644
index 0000000..cf9c7a7
--- /dev/null
+++ b/app/models/order.py
@@ -0,0 +1,43 @@
+from sqlalchemy import Column, Integer, String, Float, ForeignKey, DateTime, Enum
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+import enum
+
+from app.db.base_class import Base
+
+
+class OrderStatus(str, enum.Enum):
+    pending = "pending"
+    processing = "processing"
+    shipped = "shipped"
+    delivered = "delivered"
+    cancelled = "cancelled"
+
+
+class Order(Base):
+    id = Column(Integer, primary_key=True, index=True)
+    order_date = Column(DateTime, default=func.now())
+    status = Column(Enum(OrderStatus), default=OrderStatus.pending)
+    total_amount = Column(Float, default=0.0)
+    notes = Column(String, nullable=True)
+    
+    # Foreign keys
+    user_id = Column(Integer, ForeignKey("user.id"), nullable=False)
+    
+    # Relationships
+    user = relationship("User", back_populates="orders")
+    order_items = relationship("OrderItem", back_populates="order", cascade="all, delete-orphan")
+
+
+class OrderItem(Base):
+    id = Column(Integer, primary_key=True, index=True)
+    quantity = Column(Integer, nullable=False)
+    unit_price = Column(Float, nullable=False)
+    
+    # Foreign keys
+    order_id = Column(Integer, ForeignKey("order.id"), nullable=False)
+    product_id = Column(Integer, ForeignKey("product.id"), nullable=False)
+    
+    # Relationships
+    order = relationship("Order", back_populates="order_items")
+    product = relationship("Product", back_populates="order_items")
\ No newline at end of file
diff --git a/app/models/product.py b/app/models/product.py
new file mode 100644
index 0000000..6993bca
--- /dev/null
+++ b/app/models/product.py
@@ -0,0 +1,25 @@
+from sqlalchemy import Column, Integer, String, Float, ForeignKey, Boolean
+from sqlalchemy.orm import relationship
+
+from app.db.base_class import Base
+
+
+class Product(Base):
+    id = Column(Integer, primary_key=True, index=True)
+    name = Column(String, index=True, nullable=False)
+    description = Column(String, nullable=True)
+    sku = Column(String, index=True, unique=True, nullable=False)
+    barcode = Column(String, index=True, unique=True, nullable=True)
+    price = Column(Float, nullable=False)
+    cost = Column(Float, nullable=False)
+    is_active = Column(Boolean, default=True)
+    
+    # Foreign keys
+    category_id = Column(Integer, ForeignKey("category.id"), nullable=True)
+    supplier_id = Column(Integer, ForeignKey("supplier.id"), nullable=True)
+    
+    # Relationships
+    category = relationship("Category", back_populates="products")
+    supplier = relationship("Supplier", back_populates="products")
+    inventory_items = relationship("InventoryItem", back_populates="product")
+    order_items = relationship("OrderItem", back_populates="product")
\ No newline at end of file
diff --git a/app/models/supplier.py b/app/models/supplier.py
new file mode 100644
index 0000000..cbf88e5
--- /dev/null
+++ b/app/models/supplier.py
@@ -0,0 +1,16 @@
+from sqlalchemy import Column, Integer, String
+from sqlalchemy.orm import relationship
+
+from app.db.base_class import Base
+
+
+class Supplier(Base):
+    id = Column(Integer, primary_key=True, index=True)
+    name = Column(String, index=True, nullable=False)
+    contact_name = Column(String, nullable=True)
+    email = Column(String, nullable=True)
+    phone = Column(String, nullable=True)
+    address = Column(String, nullable=True)
+    
+    # Relationships
+    products = relationship("Product", back_populates="supplier")
\ No newline at end of file
diff --git a/app/models/user.py b/app/models/user.py
new file mode 100644
index 0000000..52870c1
--- /dev/null
+++ b/app/models/user.py
@@ -0,0 +1,16 @@
+from sqlalchemy import Boolean, Column, Integer, String
+from sqlalchemy.orm import relationship
+
+from app.db.base_class import Base
+
+
+class User(Base):
+    id = Column(Integer, primary_key=True, index=True)
+    full_name = Column(String, index=True)
+    email = Column(String, unique=True, index=True, nullable=False)
+    hashed_password = Column(String, nullable=False)
+    is_active = Column(Boolean(), default=True)
+    is_superuser = Column(Boolean(), default=False)
+
+    # Relationships
+    orders = relationship("Order", back_populates="user")
\ No newline at end of file
diff --git a/app/schemas/__init__.py b/app/schemas/__init__.py
new file mode 100644
index 0000000..25a1fff
--- /dev/null
+++ b/app/schemas/__init__.py
@@ -0,0 +1,7 @@
+from .token import Token, TokenPayload
+from .user import User, UserCreate, UserInDB, UserUpdate
+from .category import Category, CategoryCreate, CategoryInDB, CategoryUpdate
+from .supplier import Supplier, SupplierCreate, SupplierInDB, SupplierUpdate
+from .product import Product, ProductCreate, ProductInDB, ProductUpdate
+from .inventory import InventoryItem, InventoryItemCreate, InventoryItemInDB, InventoryItemUpdate
+from .order import Order, OrderCreate, OrderInDB, OrderUpdate, OrderItem, OrderItemCreate, OrderItemInDB, OrderItemUpdate
\ No newline at end of file
diff --git a/app/schemas/category.py b/app/schemas/category.py
new file mode 100644
index 0000000..7159056
--- /dev/null
+++ b/app/schemas/category.py
@@ -0,0 +1,36 @@
+from typing import Optional
+
+from pydantic import BaseModel
+
+
+# Shared properties
+class CategoryBase(BaseModel):
+    name: Optional[str] = None
+    description: Optional[str] = None
+
+
+# Properties to receive via API on creation
+class CategoryCreate(CategoryBase):
+    name: str
+
+
+# Properties to receive via API on update
+class CategoryUpdate(CategoryBase):
+    pass
+
+
+class CategoryInDBBase(CategoryBase):
+    id: int
+
+    class Config:
+        orm_mode = True
+
+
+# Additional properties to return via API
+class Category(CategoryInDBBase):
+    pass
+
+
+# Additional properties stored in DB
+class CategoryInDB(CategoryInDBBase):
+    pass
\ No newline at end of file
diff --git a/app/schemas/inventory.py b/app/schemas/inventory.py
new file mode 100644
index 0000000..a2dfed1
--- /dev/null
+++ b/app/schemas/inventory.py
@@ -0,0 +1,42 @@
+from typing import Optional
+from datetime import datetime
+
+from pydantic import BaseModel, Field
+
+
+# Shared properties
+class InventoryItemBase(BaseModel):
+    product_id: Optional[int] = None
+    quantity: Optional[int] = 0
+    location: Optional[str] = None
+    min_stock_level: Optional[int] = 0
+    max_stock_level: Optional[int] = 0
+
+
+# Properties to receive via API on creation
+class InventoryItemCreate(InventoryItemBase):
+    product_id: int
+    quantity: int = Field(..., ge=0)
+
+
+# Properties to receive via API on update
+class InventoryItemUpdate(InventoryItemBase):
+    pass
+
+
+class InventoryItemInDBBase(InventoryItemBase):
+    id: int
+    last_updated: datetime
+
+    class Config:
+        orm_mode = True
+
+
+# Additional properties to return via API
+class InventoryItem(InventoryItemInDBBase):
+    pass
+
+
+# Additional properties stored in DB
+class InventoryItemInDB(InventoryItemInDBBase):
+    pass
\ No newline at end of file
diff --git a/app/schemas/order.py b/app/schemas/order.py
new file mode 100644
index 0000000..00724c3
--- /dev/null
+++ b/app/schemas/order.py
@@ -0,0 +1,71 @@
+from typing import Optional, List
+from datetime import datetime
+
+from pydantic import BaseModel, Field
+
+from app.models.order import OrderStatus
+
+
+# OrderItem schemas
+class OrderItemBase(BaseModel):
+    product_id: Optional[int] = None
+    quantity: Optional[int] = None
+    unit_price: Optional[float] = None
+
+
+class OrderItemCreate(OrderItemBase):
+    product_id: int
+    quantity: int = Field(..., gt=0)
+    unit_price: float = Field(..., gt=0)
+
+
+class OrderItemUpdate(OrderItemBase):
+    pass
+
+
+class OrderItemInDBBase(OrderItemBase):
+    id: int
+    order_id: int
+
+    class Config:
+        orm_mode = True
+
+
+class OrderItem(OrderItemInDBBase):
+    pass
+
+
+class OrderItemInDB(OrderItemInDBBase):
+    pass
+
+
+# Order schemas
+class OrderBase(BaseModel):
+    status: Optional[OrderStatus] = None
+    notes: Optional[str] = None
+
+
+class OrderCreate(OrderBase):
+    order_items: List[OrderItemCreate]
+
+
+class OrderUpdate(OrderBase):
+    pass
+
+
+class OrderInDBBase(OrderBase):
+    id: int
+    order_date: datetime
+    total_amount: float
+    user_id: int
+
+    class Config:
+        orm_mode = True
+
+
+class Order(OrderInDBBase):
+    order_items: List[OrderItem] = []
+
+
+class OrderInDB(OrderInDBBase):
+    pass
\ No newline at end of file
diff --git a/app/schemas/product.py b/app/schemas/product.py
new file mode 100644
index 0000000..19054b7
--- /dev/null
+++ b/app/schemas/product.py
@@ -0,0 +1,46 @@
+from typing import Optional
+
+from pydantic import BaseModel, Field
+
+
+# Shared properties
+class ProductBase(BaseModel):
+    name: Optional[str] = None
+    description: Optional[str] = None
+    sku: Optional[str] = None
+    barcode: Optional[str] = None
+    price: Optional[float] = None
+    cost: Optional[float] = None
+    is_active: Optional[bool] = True
+    category_id: Optional[int] = None
+    supplier_id: Optional[int] = None
+
+
+# Properties to receive via API on creation
+class ProductCreate(ProductBase):
+    name: str
+    sku: str
+    price: float = Field(..., gt=0)
+    cost: float = Field(..., ge=0)
+
+
+# Properties to receive via API on update
+class ProductUpdate(ProductBase):
+    pass
+
+
+class ProductInDBBase(ProductBase):
+    id: int
+
+    class Config:
+        orm_mode = True
+
+
+# Additional properties to return via API
+class Product(ProductInDBBase):
+    pass
+
+
+# Additional properties stored in DB
+class ProductInDB(ProductInDBBase):
+    pass
\ No newline at end of file
diff --git a/app/schemas/supplier.py b/app/schemas/supplier.py
new file mode 100644
index 0000000..09a9abb
--- /dev/null
+++ b/app/schemas/supplier.py
@@ -0,0 +1,39 @@
+from typing import Optional
+
+from pydantic import BaseModel, EmailStr
+
+
+# Shared properties
+class SupplierBase(BaseModel):
+    name: Optional[str] = None
+    contact_name: Optional[str] = None
+    email: Optional[EmailStr] = None
+    phone: Optional[str] = None
+    address: Optional[str] = None
+
+
+# Properties to receive via API on creation
+class SupplierCreate(SupplierBase):
+    name: str
+
+
+# Properties to receive via API on update
+class SupplierUpdate(SupplierBase):
+    pass
+
+
+class SupplierInDBBase(SupplierBase):
+    id: int
+
+    class Config:
+        orm_mode = True
+
+
+# Additional properties to return via API
+class Supplier(SupplierInDBBase):
+    pass
+
+
+# Additional properties stored in DB
+class SupplierInDB(SupplierInDBBase):
+    pass
\ No newline at end of file
diff --git a/app/schemas/token.py b/app/schemas/token.py
new file mode 100644
index 0000000..69541e2
--- /dev/null
+++ b/app/schemas/token.py
@@ -0,0 +1,12 @@
+from typing import Optional
+
+from pydantic import BaseModel
+
+
+class Token(BaseModel):
+    access_token: str
+    token_type: str
+
+
+class TokenPayload(BaseModel):
+    sub: Optional[int] = None
\ No newline at end of file
diff --git a/app/schemas/user.py b/app/schemas/user.py
new file mode 100644
index 0000000..aa88b84
--- /dev/null
+++ b/app/schemas/user.py
@@ -0,0 +1,39 @@
+from typing import Optional
+
+from pydantic import BaseModel, EmailStr
+
+
+# Shared properties
+class UserBase(BaseModel):
+    email: Optional[EmailStr] = None
+    is_active: Optional[bool] = True
+    is_superuser: bool = False
+    full_name: Optional[str] = None
+
+
+# Properties to receive via API on creation
+class UserCreate(UserBase):
+    email: EmailStr
+    password: str
+
+
+# Properties to receive via API on update
+class UserUpdate(UserBase):
+    password: Optional[str] = None
+
+
+class UserInDBBase(UserBase):
+    id: Optional[int] = None
+
+    class Config:
+        orm_mode = True
+
+
+# Additional properties to return via API
+class User(UserInDBBase):
+    pass
+
+
+# Additional properties stored in DB
+class UserInDB(UserInDBBase):
+    hashed_password: str
\ No newline at end of file
diff --git a/kubernetes/secrets.yaml b/kubernetes/secrets.yaml
new file mode 100644
index 0000000..42bff2f
--- /dev/null
+++ b/kubernetes/secrets.yaml
@@ -0,0 +1,10 @@
+apiVersion: v1
+kind: Secret
+metadata:
+  name: inventory-api-secrets
+type: Opaque
+data:
+  # These are example base64-encoded values. You should replace them with actual values.
+  # For example, to generate a value: echo -n "your-secret-key" | base64
+  secret-key: eW91ci1zZWNyZXQta2V5LWZvci1wcm9kdWN0aW9u
+  admin-password: YWRtaW4tcGFzc3dvcmQ=
\ No newline at end of file
diff --git a/kubernetes/service.yaml b/kubernetes/service.yaml
new file mode 100644
index 0000000..28405e0
--- /dev/null
+++ b/kubernetes/service.yaml
@@ -0,0 +1,15 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: prod-pod-service
+  labels:
+    app: inventory-api
+spec:
+  type: ClusterIP
+  ports:
+  - port: 80
+    targetPort: 8000
+    protocol: TCP
+    name: http
+  selector:
+    app: inventory-api
\ No newline at end of file
diff --git a/main.py b/main.py
new file mode 100644
index 0000000..23435f7
--- /dev/null
+++ b/main.py
@@ -0,0 +1,58 @@
+import uvicorn
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+from starlette.responses import RedirectResponse
+
+from app.api.api_v1.api import api_router
+from app.core.config import settings
+
+app = FastAPI(
+    title=settings.PROJECT_NAME,
+    description="Small Business Inventory Management System API",
+    version="0.1.0",
+    openapi_url="/openapi.json",
+    docs_url="/docs",
+    redoc_url="/redoc",
+)
+
+# Set up CORS
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+# Include API router
+app.include_router(api_router, prefix=settings.API_V1_STR)
+
+
+@app.get("/", tags=["Root"])
+async def root():
+    """
+    Root endpoint returning basic service information.
+    """
+    return {
+        "title": settings.PROJECT_NAME,
+        "documentation": "/docs",
+        "health": "/health"
+    }
+
+
+@app.get("/health", tags=["Health"])
+async def health():
+    """
+    Health check endpoint.
+    """
+    return {"status": "healthy"}
+
+
+# Redirect to docs
+@app.get("/docs-redirect")
+async def docs_redirect():
+    return RedirectResponse(url="/docs")
+
+
+if __name__ == "__main__":
+    uvicorn.run("main:app", host="0.0.0.0", port=8000, reload=True)
\ No newline at end of file
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..e708027
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,11 @@
+fastapi>=0.68.0,<0.69.0
+pydantic>=1.8.0,<2.0.0
+uvicorn>=0.15.0,<0.16.0
+SQLAlchemy>=1.4.23,<1.5.0
+alembic>=1.7.5,<1.8.0
+python-jose[cryptography]>=3.3.0,<3.4.0
+passlib[bcrypt]>=1.7.4,<1.8.0
+python-multipart>=0.0.5,<0.0.6
+email-validator>=1.1.3,<1.2.0
+python-dotenv>=0.19.1,<0.20.0
+ruff>=0.0.262
\ No newline at end of file