If you're among the third of Americans who have some trouble staying asleep through the night, we have good news: maybe you don't have to. It's totally possible to plan a sleep schedule that keeps you rested even if you hit a three-hour insomnia patch every night. In fact, that's how pretty much everyone slept through most of history.
We've Had First Sleep, But What About Second Sleep?
A Siesta for the Rest of Us
Key Facts In This Video
There is no solid scientific consensus on why we sleep. 01:56
Black rhinos sleep for one to two hours laying down, and three to four hours standing up. 04:23
Dolphins engage in unihemispheric sleep, which means that one half of the brain is resting while the other half is alert. 08:01
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