Cows can sleep standing up, but they can only dream lying down.
745
If you hold farts in during the day, they'll just come out when you sleep.
16
"Dysania" is the state of finding it hard getting up out of bed in the morning.
33
The human brain is more active during sleep than during the day.
28
In China, teachers allow children to sleep in class for around 20 minutes to help improve their learning.
13
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23