[
Science,
1984]
Within the past few years researchers have finally begun to be able to peer inside a hitherto impenetrable black box, namely, the development of complex organisms. The genes that control the commitment of embryonic cells to specific fates are now being found and characterized. A case in point is reported in this issue of Science (p. 409). Victor Ambros of Harvard University and H. Robert Horvitz of Massachusetts Institute of Technology have identified genes that affect the timing of developmental events in the roundworm Caenorhabditis elegans.