Hitoyoshi Yasuo is a group leader at the Laboratoire de Biologie du Développement de Villefranche-sur-Mer, affiliated with the Université Pierre et Marie Curie. One of the fundamental questions in developmental biology is how a cell can give rise to two sister cells, each of which undertakes a distinct developmental pathway. Understanding how cells receive, process and respond to information from their environment is vital to our understanding of how cell fate choices are made. Specifically, Hitoyoshi Yasuo is asking how the egg (a single cell) can ultimately generate the wide variety of different cell types during the process of embryogenesis. He is using early development of the ascidian Ciona intestinalis as a model system to ask these questions.