Here's why:

* Flattened stack of tubular membranes: The Golgi apparatus is composed of a series of flattened, disc-shaped sacs called cisternae, which are stacked upon each other like a stack of pancakes.

* Modifies and packages proteins: The Golgi apparatus receives proteins from the endoplasmic reticulum (ER). As these proteins move through the Golgi, they undergo various modifications, such as glycosylation (adding sugars) and phosphorylation (adding phosphate groups).

* Packages proteins into vesicles: Once modified, the proteins are packaged into small membrane-bound sacs called vesicles.

* Transports to other organelles or out of the cell: These vesicles then transport the proteins to their final destinations, which can be other organelles within the cell, or the cell's exterior for secretion.

Let me know if you have any other questions!