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.
After one to two cycles of NREM sleep, REM is entered at about 60 to 90 minutes. The first one third of the night is mostly deep sleep (NREM stages 3 and 4). The last one half of the night is predominately stage 2 NREM and REM. In newborns, the amount of sleep is divided fairly equally between night and day.