A discussion of the neural crest and neural crest cells, dealing with their discovery, their embryological and evolutionary origins, their cellular derivatives - in both agnathan and jawed vertebrates or gnathostomes - and the broad topics of migration and differentiation in normal development. The book also considers what goes wrong when development is misdirected by mutations, or by exposure of embryos to exogenous agents such as drugs, alcohol, or excess vitamin A, and includes discussions of tumours and syndromes and birth defects involving neural crest cells.