History of sleep & how man slept before the light bulb was invented. Recent research shows that when given 14 hours of darkness in which to sleep 2 hours are spent falling asleep and then 2 stages of 4 hrs. each of sleep follow with a wake up period of an hr. or so in between. Now due to Thomas Edison's invention of the light bulb we are limited to an 8 hour bedtime and erroneously think waking in the night is a disorder.
Many of us know that not getting enough sleep each night is bad for our health. But some of us underestimate how lack of sleep affects the human brain. This infographic from Mic.com covers what sleep deprivation does to your brain: