The central aim of this laboratory is to understand some aspects of how spatial pattern emerges during embryonic growth and development. While we study a number of biological systems by a variety of techniques, there is an underlying theme to our work. We wish to know something of the directional signals that guide cells to destinations or determine their polarity, the mechanism by which cells perceive these signals, and the nature of the intracellular responses to the signals. Inevitably, we can consider only a subset of the vast possibilities. In particular, we are interested in the role of endogenous electrical fields and light as directional signals, and calcium as the intracellular response element. Our approach is a physiological one that involves extensive microinjection of living cells and computer-assisted imaging of the cells in order to determine the distribution of Ca2+ in the cells. A brief overview of our current research on three biological systems follows, including links to more detailed descriptions.