zZz

It takes about fifteen minutes to fall asleep. Then your sleep pass by cycles of 90 minutes and each cycle have within 2 phases.

Phase 1: Your brain waves down its frequency and enter into a deep sleep, also known as non-REM sleep.
Phase 2: The frequency increases and begins the REM sleep. That's when you start to dream.

Try not to break one of these cycles or you will wake up tired and cranky.

zZz helps you on completing sleep cycles and wake up refreshed.