It's 3 or 4 in the morning. You open your eyes suddenly, without a sound, without a nightmare, for no apparent reason. The house is silent, the world seems frozen, and yet… you are awake, unable to fall back asleep immediately.
If this scene sounds familiar, you're part of the silent majority. Millions of people experience these nighttime awakenings, almost always at the same time. This phenomenon, which has inspired myths, spiritual beliefs, and anxieties, is nevertheless based on very concrete mechanisms of the body and brain.
