There are five different stages in sleep. Stages one and two consist of Alpha wave where the body drops into a light sleep and the core body temperature decreases. Following theses stages the sleep waves move to Theata waves for stages three and four. Within these stages the bodys metabolism is slowed and the growth hormone is secreated. Lastly going into stage five the sleep waves turn into Delta waves whereby it is believed that most dreaming occurs as it is REM sleep (Rapid Eye Movement). This stage is where the body is almost paralysed by sleep however the brain is most active. This five stage cycle is repeated every 90 minutes.
