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
Honeybees never sleep.
276
One reason that kittens sleep so much is because a growth hormone is released only during sleep.
212
You forget 90% of your dreams.
256
The human brain is more active during sleep than during the day.
28
You burn more calories sleeping than you do watching television.
348