A molecule is the smallest particle in a chemical element or compound that has the chemical properties of that element or compound. Molecules are made up of atom s that are held together by chemical bonds.
Some studies have shown that your deep sleep should at least be 20% of your overall sleep. It means that since most adults need 8-9 hours of sleep, they will need about 1.6-1.8 hours of deep sleep to feel fully functional next day. However, the time of deep sleep is changed and that's mainly due to the change in the sleep need of different group of people. For instance: Age Group.
Updated December 16, 2014. There are five phases of sleep: stages 1, 2, 3, 4 and REM (rapid eye movement). Usually when you are sleeping, you begin at stage 1 and go through each stage until reaching REM sleep, and then you begin the cycle again. Each complete sleep cycle takes from 90 to 110 minutes. Your brain acts differently in each stage of sleep. In some of the stages, your body may make movements, but in others your arms and legs will be immobile. Having good sleep habits will make sure you get each type of sleep that you need.