During the past four years, the field of developmental biology has begun a new metamorphosis. The Ninth Edition of Developmental Biology mirrors this shift with a wholly revised text, over 600 new literature citations, and substantial reorganization of content. The introductory section has been streamlined from six chapters to three-one each on developmental anatomy, the mechanisms of gene regulation during differentiation, and cell-cell communication during morphogenesis. Another new feature is the addition of short part openers that address key concerns in developmental biology. These provide an introduction to the subsequent chapters, telling the reader what to expect and placing that information into a specific context. Each chapter ends with a guide to Web-based resources relevant to that chapter's content, and the Ninth Edition is the first to include a glossary of key terms. Some of the new material in this edition includes: mesenchymal and induced pluripotent stem cells; the transdifferentiation of pancreatic cells; new data on sea urchin micromere specification; the mechanisms whereby Sry and Wnt signaling determine mammalian sex; the memory of cell fate during amphibian limb regeneration; how bats got their wings and how dachshunds got their short legs. This completely updated text includes fundamental new material that alters what we teach in developmental biology courses. Included inside every new copy of the book is an online access code for Mary Tyler and Ron Kozlowski's remarkable resource, DevBio Laboratory: Vade Mecum3. (Online access may also be purchased separately.) The book also offers a Companion Website (www.devbio.com). Cross-referenced throughout the textbook, this resource provides more information for advanced students, historical, philosophical, and ethical perspectives on issues in developmental biology, videos, interviews, Web links, and updates. The website includes the full bibliography of literature cited in the book, most of which are linked to their PubMed citations. Also, for the Ninth Edition, Susan Singer's chapter on plant developmental biology has been moved to this location.