Part I. Patterns and processes of becoming: a framework for understanding animal development -- 1. Making new bodies: mechanisms of developmental organization -- 2. Specifying identity: mechanisms of developmental patterning -- 3. Differential gene expression: mechanisms of cell differentiation -- 4. Cell-to-cell communication: mechanisms of morphogenesis -- 5. Stems cells: their potential and their niches -- Part II. Gametogenesis and fertilization: the circle of sex -- 6. Sex determination and gametogenesis -- 7. Fertilization: beginning a new organism -- Part III. Early development: cleavage, gastrulation, and axis formation -- 8. Rapid specification in snails and nematodes -- 9. The genetics of axis specification in Drosophila -- 10. Sea urchins and tunicates: deuterostome invertebrates -- 11. Amphibians and fish -- 12. Birds and mammals -- Part IV. Building with ectoderm: the vertebrate nervous system and epidermis -- 13. Neural tube formation and patterning -- 14. Brain growth -- 15. Neural crest cells and axonal specificity -- 16. Ectodermal placodes and the epidermis -- Part V. Building with mesoderm and endoderm: organogenesis -- 17. Paraxial mesoderm: the somites and their derivatives -- 18. Intermediate and lateral plate mesoderm: heart, blood, and kidneys -- 19. Development of the tetrapod limb -- 20. The endoderm: tubes and organs for digestion and respiration -- Part VI. Postembryonic development -- 21. Metamorphosis: the hormonal reactivation of development -- 22. Regeneration -- 23. Aging and senescence -- Part VII. Development in wider contexts -- 24. Development in health and disease: birth defects, endocrine disruptors, and cancer -- 25. Development and the environment: biotic, abiotic, and symbiotic regulation of development -- 26. Development and evolution: developmental mechanisms of evolutionary change.