This book provides a broad introduction to the fascinating subject of sleep, a behavioral state in which human beings spend a third of their life span, and a topic which interests not only the specialist but also the layperson. Everybody knows that well-being also depends on undisturbed, normal sleep. The Physiologic Nature of Sleep is self-contained in presentation. It may be used as an advanced textbook by graduate students and even ambitious undergraduates in biology, medicine and psychology. It is also suitable for the expert hypnologist who wishes to have an overview of some of the classic and fundamental achievements in sleep research. The explanations in the book are detailed enough to capture the interest of the curious reader, and complete enough to provide the necessary background material needed to go further into the subject and explore the research literature.