Is it possible to imagine life without sleep? Perhaps you can, but this is closer to science fiction. During the course of a day, we sleep, depending on the individual, 20-30% of the time. If something takes up so much time, it may be due either to a pleasure to which we are able to devote an unlimited amount of time, or to a duty we perform because we have an inner conviction of its necessity. Sleep is just such a unique combination of the two poles: duty and pleasure. What happens to the brain during sleep? When we fall asleep, does the 'brain switch off'?