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.
The loss of deep sleep with age. One of the unfortunate effects of age is that as we get older we spend less time in deep sleep. While healthy people in their 20s spend 20% of the night in Stage 3, a typical 40 or 50 year old spends only 10% in that stage.