Blue light fends off drowsiness in the middle of the night, which could be useful to people who work at night.
240
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
"Dysania" is the state of finding it hard getting up out of bed in the morning.
33
There's a love mattress that is specifically designed for couples who sleep on each other's arms.
12
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23