During your sleep time you go through many phases (or stages of sleep). The first stage you go through is when your brain releases theta and beta waves. Stage 2 is when the brain increases brain wave frequency. Stage 3 is when you start to dream, stage 4 is when your body stimulates growth. Finally, stage 5 is when you enter the REM stage. This stage is the most active part of your day. During this part of sleep you are very deep in sleeping.