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
Studies show that the colder the room you sleep in, the more likely you are to have a bad dream.
28
The harder you concentrate on falling asleep, the less likely you are to fall asleep.
34
In China, teachers allow children to sleep in class for around 20 minutes to help improve their learning.
13
You forget 90% of your dreams.
256
You burn more calories sleeping than you do watching television.
348