Volume 3 of the Carotenoids series moves into the area of biochemistry & biology, concentrating on how the carotenoid molecules are formed in nature & utilized or modified by living organisms. Animals cannot biosynthesize carotenoids de novo. Dietary carotenoids provide most of the vitamin A that is vital for health & development in humans & other mammals. The formation of vitamin A & the absorption, transport & deposition of carotenoids in tissues in mammals are described, followed by a detailed account of the diverse metabolic reactions by which dietary carotenoids undergo structural & stereochemical changes in birds, fish & invertebrate animals. The relevance of carotenoids for use as markers to trace food chains is also discussed. In keeping with the philosophy of the carotenoid series guidance on the application of some of the most important experimental procedures for studies of biosynthesis & metabolism are given in the final chapter. The information presented & analyzed by expert authors in this volume will serve as a useful reference source, & give valuable guidance on practical strategies & procedures, as a foundation for the exciting advances that can be expected in carotenoid biosynthesis & metabolism in the next few years.