Complex organisms are composed of small units named cells, which are regularly assembled to form tissues, organs, and finally individual organisms. To elucidate the mechanism of the structure formation, Townes and Holtfreter proposed a famous model called selective adhesion hypothesis in 1955. However, the molecular mechanism had remained elusive for a long time. Eventually, Takeichi clarified the Ca2+-dependent cell adhesion mechanism and his group identified the responsible protein, cadherin. Since then, many cadherins were identified from various tissues of different organisms. Now, it is well accepted that many cadherins play various roles in a variety of tissues and organs, although the details are still uncharacterized.