Blue light fends off drowsiness in the middle of the night, which could be useful to people who work at night.
240
Sea otters hold hands while sleeping so they don’t drift away from each other.
104
The human brain is more active during sleep than during the day.
28
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
There's a love mattress that is specifically designed for couples who sleep on each other's arms.
12