Why do I need sleep?

Scientists do not know exactly why people need sleep, but studies show that sleep is necessary for survival. Sleep appears to be necessary for the nervous system to work properly. While too little sleep one night may leave us feeling drowsy and unable to concentrate the next day, a long period of too little sleep leads to poor memory and physical performance. Hallucinations (seeing things that aren’t really there), vision problems, and mood swings may develop if sleep deprivation continues.