Cell-cell adhesion in the various types of intercellular junctions of differentiated tissues is relatively stable and permanent. In migrating cells of embryos, or in wound closure, inflammatory responses and tumors of adult tissues, however, bonds between cells are made and broken and made again, i.e., cell-cell adhesions are transient and reversible. These nonjunctional contacts lack the organized structure of intercellular junctions, but may initiate their tissue-specific formation during development. Investigation of dynamic, nonjunctional cell-cell adhesions has been hampered by the asynchronous and heterogeneous distribution of these transient contacts among groups of moving cells. We recently discovered a novel system of reversible cell adhesion in a differentiated tissue that overcomes this difficulty. Here I review our current knowledge of this system, particularly its unique experimental advantages for investigating the mechanisms and control of dynamic cell adhesion.