Close and daily, sometimes comical but often tragic, sleepiness takes an important place in our lives. Suddenly falling asleep, sometimes with their eyes still open, affects more than 10% of the population. The leading cause of fatal accidents on motorways, drowsiness is also prevalent in the world of work. A silent, irrepressible phenomenon... a flaw in a system of performance, speed, reactivity. So what is happening in our brain? Can we control the conditions of sleepiness? By working on sleep and especially on the functioning of wakefulness, researchers are trying to understand the biological and environmental mechanisms that keep humans at the peak of their abilities. After a clear technological improvement, it turns out that man, having become an expert and process controller, finds it very difficult to focus his attention over time.