The CyGenTiG research programme brings together three different fields of science and technology to create a new strategy for biological control. From biological science, there is optogenetics, a way of controlling cell behaviour with light. From physical and mathematical sciences there is bidirectional microscopy, in which light is used both to pass information to cells and to retrieve information from cells, all under computer control. From that hybrid of biology and engineering called synthetic biology, there are genetic modules that take control of cell behaviour. Our task is to combine these powerful technologies to develop new ways of bringing basic biological processes under human command.