Watch this informative video on why some scientists think people only need 4 hours of sleep.
I think you would get exhausted only having 4hours of sleep consistently every night, but according to researcher Ying-Hui Fu some people are "natural short sleepers."
According to Dr.Fu, two rare genes allow some people to feel rested after 4 or 5 hours of sleep per night.
How many hours a sleep a night do you need to feel rested?
(WIRED)