FOCAL POINT Embryonic stem cells start to differentiate unless they remain in contact with surrounding cells. (L-R) Dong Li, Jiaxi Zhou, Fei Wang, and colleagues (not shown) discovered that a regulatory network containing E-cadherin, NMMIIA, and p120-catenin makes the cells gregarious. The image above shows NMMIIA (green) and E-cadherin (red) in a colony of human embryonic stem cells.