The model used to explain the structure of the cell membrane is called the Fluid Mosaic Model.

Here's why it's called that:

* Fluid: The phospholipid bilayer is not rigid, but rather fluid and flexible, allowing molecules to move laterally within the membrane.

* Mosaic: The membrane is composed of a variety of different components, including phospholipids, proteins, cholesterol, and carbohydrates, all arranged in a mosaic-like pattern.

This model was proposed by S. Jonathan Singer and Garth L. Nicolson in 1972 and has been the accepted model of membrane structure ever since.