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
Quick naps not only improve your alertness, but they also help in decision making, creativity and sensory perception.
149
Sleeping on your stomach can induce weirder, scarier, and sexier dreams.
22
You burn more calories sleeping than you do watching television.
348
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
In China, teachers allow children to sleep in class for around 20 minutes to help improve their learning.
13
Sleeping on the job is acceptable in Japan. It is viewed as exhaustion from working hard. Some people fake it to look committed to their job.
57
The harder you concentrate on falling asleep, the less likely you are to fall asleep.
34