Sleep is one of the most important things in our life. Just like food and water we need it to survive. Sleep can be put into two categories that are REM sleep and NREM sleep. REM stands for rapid eye movement, therefore NREM means non-rapid eye movement. NREM consists of three stages. NREM last for 75% of the night and REM last for the other 25%.
The first stage consist of light sleep and is when it is the easiest to wake up. It is when you drift in and out of sleep. The second stage is when your body temperature lowers and your heart rate slows down. The third stage is when the body goes into deep sleep and when sleep walking occurs. It is also when energy is restored, breathing is slower, and tissue growth and repair occurs.
REM sleep first happens around 90 minutes after falling asleep and repeats around every 90 minutes. The First REM cycle last around 10 minutes with each cycle getting longer until it last about an hour. This is also the part of sleep when the most vivid dreams happen, which is why during this stage our muscle become paralyzed to prevent us from acting out our dreams.