The explosion of new knowledge in human reproduction and development is akin to the population explosion, thus making it difficult to be well informed in either the biological or behavioral aspects of postnatal human development. The editor of this text has provided students and practitioners alike with an authoritative review of many fields—most of them in the postnatal period of development, including anatomy, genetics, biochemistry, physical growth, physiology, psychology, and behavior. In order to do this, he selected a team of 29 experts drawn from the front ranks of their respective fields and obtained from them a uniformly high level of performance. They all seem to have had the same idea in mind—to give the reader a succinct, factual, up-to-date review of human development in their special area of interest. In addition, each author amply illustrated his chapter with tables and graphs and gave references to the principal sources.