When you eat, your food is broken down and sent to the cells of your body. These cells take in the food and grow bigger. Then each cell divides and becomes two cells exactly like itself. Each cell divides again, making four cells, and so on. This cell division goes on day and night. As the number of cells in your body becomes greater, you grow bigger and bigger.
When you are about 20 years old, a change takes place. Your plan for growing up is completed. From then on, your body stops growing taller, but the foods you eat keep your body in good running order, and help repair any worn-out parts. After you reach your full height, you may get fatter or thinner, but you won’t get any taller.