Some people have a "natural alarm clock" allowing them to wake up when they want. This is actually caused by a burst of the stress hormone adrenocorticotropin.
15
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
You forget 90% of your dreams.
256
The higher someone’s I.Q. the more likely they are to be sleep deprived.
29
The strangers in your dreams are actually people that you've seen in real life.
50
In China, teachers allow children to sleep in class for around 20 minutes to help improve their learning.
13
Lack of water is the #1 trigger of daytime fatigue.
148