This an overview of that most vital, most underrated and most elusive of human activities, that draws on both cutting-edge neuroscience and classic literature. We spend one third of our lives asleep, but know hardly anything about it, and can remember so little of it as we come out of it. Why? This text seeks to answer questions such as: does sleeping keep us sane?; are dreams the place we go to resolve our problems, emasculate our fears and rehearse our hopes?; why are we paralysed when we dream?; why did sleep evolve?; and are we getting enough sleep?