In China, teachers allow children to sleep in class for around 20 minutes to help improve their learning.
13
Cows can sleep standing up, but they can only dream lying down.
745
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
Blue light fends off drowsiness in the middle of the night, which could be useful to people who work at night.
240
The average cat sleeps about 2/3 of the day.
203
Bats sleep 18-20 hours per day.
5
The human brain is more active during sleep than during the day.
28