The human brain is more active during sleep than during the day.
28
Bats sleep 18-20 hours per day.
5
Cows can sleep standing up, but they can only dream lying down.
745
One reason that kittens sleep so much is because a growth hormone is released only during sleep.
212
Honeybees never sleep.
276
Blue light fends off drowsiness in the middle of the night, which could be useful to people who work at night.
240
The harder you concentrate on falling asleep, the less likely you are to fall asleep.
34