The sunrise is our regular natural alarm by which we set our body clock, aligning our daily rhythms with day and night. Most of us however mix early starts, late nights and weekend lie-ins and, given such inconsistent light cues, our body clock is soon thrown out of sync. This 'social jet lag' affects many teenagers and adults who have trouble waking up for school or work and feel tired and stressed. A 'dawn simulator' can help by waking you with light, just like a sunrise. With your body clock set to run in time with your day, you'll feel brighter, more refreshed as well as naturally ready for sleep when it's night.