Adhesion of like cells is a primary feature of the architecture of many tissues. A sheet of absorptive epithelial cells, for instance, forms the lining of the small intestine, and sheets of hepatocytes two cells thick make up much of the liver. A number of cell-surface proteins (the CAMs), mediate such homophilic (like-binds-like) adhesion between cells of a single type and heterophilic adhesion between cells of different types. Most CAMs are uniformly distributed along the regions of plasma membranes that contact other cells, and the cytosol-facing domains of these proteins are usually connected to elements of the cytoskeleton.