Why we need to sleep is not actually known, but it is a topic that continues to intrigue us and it is still very much the subject of active research. The author takes an historical approach to the subject and hence largely takes a chronological view of sleep research and the scientists' ideas and their experiments. Parts one and two describe the main historical figures and their various theories and discoveries. Part three describes our current state of knowledge of sleep, arousal and waking. It discusses sleep and waking disorders and discusses the current theories behind the function of sleep. This is a book readable by anyone who has some introductory biology or psychology and has an interest in why and how we sleep it will also make an excellent book for anyone taking a course on the physiology and functions of sleep.