One reason that kittens sleep so much is because a growth hormone is released only during sleep.
212
Bats sleep 18-20 hours per day.
5
The human brain is more active during sleep than during the day.
28
Lack of water is the #1 trigger of daytime fatigue.
148
Quick naps not only improve your alertness, but they also help in decision making, creativity and sensory perception.
149
The harder you concentrate on falling asleep, the less likely you are to fall asleep.
34
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23