For decades the way of viewing of the cell membrane has changed considerably. At the beginning of the twentieth century the cell membrane was visualized as a lipid bilayer. Following researches have discovered that the cell membrane contains also proteins. In 1972 Singer and Nicolson introduced the division of membrane proteins into peripheral and integral proteins. Singer and Nicolson had also conduc-ted research on cells fusion, which have laid the foundation of the membrane model as a fluid mosaic of lipids and proteins. The Singer and Nicolson model in many aspects is still valid.