Singer and Nicolson’s fluid mosaic model is often used to describe the cell membrane’s structure.

It might be difficult to visualize how the cell membrane works. After all, the cell, cell membrane, and all of the cell's functions take place at levels too tiny for the naked eye to observe. S.J. Singer and G.L. Nicolson, two American scientists, devised the fluid mosaic model in 1972 to describe the structure and functions of the cell membrane. According to the model, the membrane is fluid in the sense that it is continually changing. Individual phospholipids travel laterally (in the same layer); nevertheless, one or more lipids may sometimes flip to the other layer.

Because lipids are pulled to one another by weak hydrophobic interactions, the bonds that they form are frequently broken. The proteins in the membrane, as well as cholesterols, move about in this sea of lipids (which occur only in animal cells). Cholesterols make the membrane less soluble, increasing its stiffness and hardness at moderate and higher temperatures. However, at lower temperatures, cholesterols separate phospholipids from one another, preventing the membrane from becoming excessively stiff.

For years, scientists differed over the importance of the structure they saw as the cell membrane. For over two centuries, membranes were seen but largely ignored as a significant component with biological function. It wasn't until the twentieth century that the importance of the cell membrane was recognized. Finally, Gorter and Grendel (1925) discovered that the membrane is "lipid-based". They expanded on the concept that this structure would have to be in a layer-like configuration.