There are two main types of sleep: REM and non-REM. Typically, dreams occur during REM sleep, when your eyes move rapidly and your body experiences involuntary paralysis.

The average person takes about 7 to 20 minutes to fall asleep. On average, humans spend roughly a third of their lives asleep.

Sleep deprivation is more than just an uncomfortable feeling—it can be fatal. The world record for the longest time without sleep is 11 days, set in 1964 by Randy Gardner.

One odd fact about the human body is that you can’t sneeze while you’re asleep.

Getting plenty of sleep helps the brain remove toxins linked to Alzheimer’s disease.

DEC2 is a genetic mutation known to allow some people to function with about 4 hours of sleep instead of the typical 8.

Members of the Silent Generation and Baby Boomers are more likely to dream in black and white because that’s what they saw on television during childhood.

Your sense of smell is significantly reduced while you’re asleep, which is one reason smoke detectors are so critical for saving lives.

Elephants sleep for about 2 hours a day—one of the shortest durations of any mammal.

Sleeping too much—generally more than 9 hours—has been linked to various health problems.