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
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
The record for the longest scientifically documented period without sleep is 264.4 hours (eleven days).
15
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
Bats sleep 18-20 hours per day.
5
The higher someone’s I.Q. the more likely they are to be sleep deprived.
29