In the preface to the first edition of Human Development we spoke of change as a principle that governs all our lives. As we said then, we change, we grow, we develop throughout our lives. The second edition of this book was different from the first, and this third edition is even more different from both earlier versions. The new edition places greater emphasis on the relationships among the different stage of the life span and among the physical, intellectual, social, and personality influences on development. The changes in this revision represent growth and development in our own thinking, as we present human development from the moment of conception until that moment at the other end of the life cycle when death ends the continuing process.