Cows can sleep standing up, but they can only dream lying down.
745
In China, teachers allow children to sleep in class for around 20 minutes to help improve their learning.
13
The human brain is more active during sleep than during the day.
28
The strangers in your dreams are actually people that you've seen in real life.
50
Sea otters hold hands while sleeping so they don’t drift away from each other.
104
The record for the longest scientifically documented period without sleep is 264.4 hours (eleven days).
15