What happens when we sleep? 

Sleep is a mysterious state which is both more active and complex than it first appears.

Not all sleep is the same. The Sleep cycle sheet shows the different types or stages we go through as we sleep:

We will move through these different types of sleep – four or five times – through the night and may wake up briefly as well. Having a good night’s sleep depends on spending enough time in deep sleep (Non-REM stage three). When you have had enough deep sleep you will wake up feeling refreshed and full of energy.