The organelle that appears as a stack of membranes is the Golgi apparatus.

Here's why:

* Structure: The Golgi apparatus is made up of flattened, membrane-bound sacs called cisternae. These cisternae are stacked on top of each other like a stack of pancakes.

* Function: The Golgi apparatus plays a crucial role in processing, packaging, and distributing proteins and lipids synthesized by the cell.