"You snooze, you lose".

Really?

No, it's exactly the opposite.

All vertebrates sleep, from fish to mammals, and birds even take naps while flying!

Moreover, even some invertebrates - like insects for example - sleep. An animal deprived of sleep dies sooner than if it lacks food, because sleep is an imperative metabolic need.

It's clear that our body regains its strength after a good sleep, but how?

The metabolism has two phases: burning (catabolism) and building (anabolism).

During the wakefulness, the body's cells burn themselves down to release the energy needed for the body to carry on with all its functions, especially the mobile ones, necessary to get food and to procreate.

But a predominant catabolism can be tolerated by the body for several hours. During sleep, the body enters in a predominantly anabolic phase, when it develops, grows, heals and builds muscle; the immune system is at its peak (that's why, when we're ill, we wake up without the cold).

Sleep is controlled by the brain, but there are many theories about what triggered it, from hormones to enzymes. Most of the night, the brain idles in a low energy state named slow-wave sleep; released from the charge of consciousness, it can effectuate a cleanup. Each night, about a quarter of the sleep time is reserved to REM sleep, during which the brain is anything but idle.

REM (rapid eye movement) is linked to vivid dreams and it seems to play an important role in consolidating memories. REM sleep must have other roles, too, because even antidepressants that suppress it won't impair memory.

Thus, during the sleep, our brain passes short term memory (RAM) into long term brain and muscle memory (Disk). That's why students who sleep perform better than those that "cram" prior to a test, and sportsmen and musicians need to sleep before competitions or concerts.

Not to mention that the lack of sleep is the cause of some 100,000 traffic accidents a year.