A brief outline is given of the impact of molecular genetics on the study of morphogenesis. Two approaches have been used, one beginning at the molecular level and applying knowledge gained in this way to observations of whole organisms; the other starting with descriptions of the organism and tracing the causes of developmental changes to cellular and then molecular events. The availability of experimentally induced mutants has facilitated the study of development, but such work must be combined with detailed information on the normal process. Comparative studies have exploited evolutionary conservation to identify functionally important gene activities, and allowed knowledge gained from one organism to be rapidly applied to other species. The successes achieved at the molecular level are impressive, but the time has come to return to studying the cells that are the real mediators of the transmission of the genetic information.

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