Watch Explorer Season 6 Episode 8 Online

An extremely rare genetic disease passed down through generations, fatal familial insomnia's (FFI) primary symptom is sleeplessness, but with a fatal twist: victims are dead within months. National Geographic delves into the science of sleep to find out why we need sleep and what happens to us when we don't get it. Witness the pioneering research inside the sleeping brain as well as the mind forbidden to rest for days at a time.