Here, for example, is an artist’s depiction of the endoplasmic reticulum. Why it has such a complex name, I cannot tell you, but it does. It’s called the ER in the patois of the street. The ER. And the endoplasmic reticulum is a series of membranes. Keep in mind, not the only membrane in the cell is the plasma membrane. Within the cytoplasm there are literally hundreds of membranes which are folded up in different ways.