A method of cryo-fracture (or freeze-fracture) is used in viewing via electron microscopy to study cell membrane structure. When breaking a frozen sample down, the membranes are fractured at their hydrophobic areas, thereby exposing the inner surfaces of lipid bilayer sheets.

The right side of the microphotograph displays the inner layer surface of a red blood cell membrane. A lot of rounded intramembranous particles are visible on this surface; they are integral membrane proteins. On the left, there are considerably fewer intramembranous particles on the outer layer surface because they are not bound by proteins of the cytoplasm there. When interacting with lipid molecules around them, the integral membrane proteins can form local microdomains of the membrane or "islands" that are called lipid rafts. The motility of these molecular aggregates is limited significantly. The concept describes the accepted fluid mosaic model of the cell membrane.