Cadherins are a superfamily of Ca2+-dependent adhesion molecules found in metazoans. Several classes of cadherins have been defined from which two - classic cadherins and Fat-like cadherins - have been studied by genetic approaches. Recent in vivo studies in Caenorhabditis elegans and Drosophila show that cadherins play an active role in a number of distinct morphogenetic processes, Classic cadherins function in epithelial polarization, epithelial sheet or tube fusion, cell migration, cell sorting, and axonal patterning. Fat-like cadherins are required for epithelial morphogenesis, proliferation control, and epithelial planar polarization.