A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
The human brain is more active during sleep than during the day.
28
Bats sleep 18-20 hours per day.
5
The harder you concentrate on falling asleep, the less likely you are to fall asleep.
34
"Dysania" is the state of finding it hard getting up out of bed in the morning.
33
In China, teachers allow children to sleep in class for around 20 minutes to help improve their learning.
13
Sea otters hold hands while sleeping so they don’t drift away from each other.
104