You forget 90% of your dreams.
256
The harder you concentrate on falling asleep, the less likely you are to fall asleep.
34
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
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