Sleep is food for the brain.
During sleep, important body functions and brain activity occur. As any parent of a teenager knows, rousing a sleeping adolescent can be, to put it mildly, difficult.
Grumpy and monosyllabic until later in the day, it can be just as much of a struggle to get your teen to go to bed at night, what with homework, instant messaging, email and general late-night wakefulness.