This sleep stage is incredibly important.

"Hearst Magazines and Yahoo may earn commission or revenue on some items through these links." There are countless sleep hacks, supplements, and cozy pajamas that may elevate your sleep game, but that ...

The following story is excerpted from TIME’s special edition, The Science of Sleep, which is available at Amazon. Anyone who has nodded off on the subway, faked alertness in a meeting at work or ...

How does your brain know when it's time to sleep? There are two main factors: Hours Awake. The longer you've been awake, the stronger your drive for sleep. Circadian Rhythm. Your body operates on a ...