Cell adhesion plays a role in allowing cells to be held together, and was a vital process for the evolution of multicellular organisms. Specialized cells group together to perform a specific task. During embryogenesis we see cells recognizing each other through the use of cell adhesion molecules (cams) which allow cells to segregate into distinct tissues. Cams are subdivided into classes based on their functions and interactions. After aggregation these cells form specialized cell junctions. These stabilize cell-cell interactions and promote communication between adjacent cells. Cams consist of cadherins, immunoglobulin (ig) family, integrins and selectins. Single-celled layers of cells in the single plane, cells in contact with neighbouring cells through cadherins, which allow specificity of adhesion, like cells recognizing other cells. Within epithelial cells, the matrix at bottom that is at cellular structure there are also transmembrane proteins that interact with the basal lamina. The apical surface contain microvilli that allow communication and adhesion.