An advanced undergraduate textbook focusing on the molecules and mechanisms which underlie the developmental process. In recent years, the genetic and molecular mechanisms underlying cellular behaviour have begun to be elucidated. Taking advantage of this new knowledge, Martinez Arias and Stewart here present developmental biology from a new standpoint: one in which the molecules and the genes that encode them, rather than the organisms, take centre stage. This is a compelling modern way of looking at developmental biology. Starting with the genetic programs that underlie development and working up allows a better understanding of the logic of development. TEACHING AIDS Online Resource Centre: www.oup.com/uk/best.