The world's first scholar toconcentrate entirely on sleep, Kleitman is universally recognized as the father of sleep research. Before him, few scientists had systematically investigated the intricacies of sleep, which had previously been dismissed as a state of quiescence. After Kleitman and colleagues demonstrated in the 1950's that sleep was a dynamic and varied process, there was an explosion of interest in sleep, in sleep re- search and, subsequently, in the treatment of sleep disorders. In 1939, he published the first major textbook on sleep, "Sleep and Wakefulness", which rapidly became the "Bible" of sleep researchers everywhere. It was replaced only by his revised and enlarged edition published in 1963. In September 1953, asa result of work in his laboratory, Kleitman and one of his students, the late Eugene Aserinsky, re- ported the discovery ofrapid eye movements (REMs) during sleep and suggested the association of these eye movements with dreaming. This discovery si often described as the beginning of modern sleep research, for ti demonstrated that there were at least two major kinds of sleep and that sleep included active brain processes. His discoveries about variations in mental alertness, made after two weeks in 1948 on the submarine known as Dogfish, demonstrated the difficulties of adjusting to shifting time schedules and emphasized the importance of the taking into conside- ration the body's regular rhythms in the scheduling of shift workers.