Cell to cell and cell to extracellular matrix adhesion play an essential role in embryogenesis, differentiation, morphological development and disease processes. Adhesion processes are affected by two reverse directional signaling: expression of adhesion molecules is regulated by inside-out signaling and the molecules transduce extracellular information into cytoplasm by "outside-in" signaling. Cadherins are a family of Ca(2+)-dependent cell-cell adhesion molecules that are important for the mutual association of vertebrate cells. During cell differentiation, for example, the amount or the nature of the cell-surface cadherins and other adhesion molecules change, affecting many aspects of cell-cell adhesion and cell migration.