The human brain is more active during sleep than during the day.
28
Quick naps not only improve your alertness, but they also help in decision making, creativity and sensory perception.
149
The average cat sleeps about 2/3 of the day.
203
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
The record for the longest scientifically documented period without sleep is 264.4 hours (eleven days).
15
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
Termites work 24 hours per day and they do not sleep.
57