Sleeping is an essential part of everyone's life yet it remains little understood is barely understood. You might think it's a relaxing recharge but in fact your brain is working harder at times overnight than when you're conscious in the day. Fresh insight into why and how we sleep has come from studying people with sleep disorders, especially sufferers of narcolepsy. The condition means that people fall asleep many times a day, completely out of the blue. A less known symptom is paralysing attacks, that can cause narcoleptics to fall to the ground - unable to move - several times a day. If a way can be found to ease their symptoms, it could open the way to helping any of us to control our sleep patterns and perhaps even to go without rest while staying alert. Gaynor Carr has been nodding off routinely since the age of seven. Her narcolepsy has made holding down a job impossible and made her question the idea of ever having children. Gary Beattie used to work in construction, until he fell asleep 7m up a ladder. He not only loses consciousness, his body becomes paralysed in a so-called cataleptic attack. Both of them say that showing emotion sparks the paralysing attacks and that has forced them to avoid laughing and crying. Bill Baird worked in finance but describes his stockbroking days as a race. The emotion of closing a deal would bring on a fit; he had constantly to hope he could get a client's signature before his almost inevitable collapse. His sleep is restless, with vivid nightmares when he is able to hear his surroundings while seeing terrifying hallucinations.