Sometimes comical but often tragic, somnolence, or sleepiness takes an important part in our lives. First cause of lethal highway accidents, drowsiness invites itself in our work. What happens with our brain ? Can we master sleepiness ? By working on the sleep and especially on the functioning of awakening, researchers try to understand the biological and environmental mechanisms that maintain humans at the top of their capacities. What if drowsiness was there to prove that we are not machines ?