It starts with cells -- cells are made up of all things in the body. Humans have 10 trillion cells. Cell membranes control the movement of substances into and out of cells, the body grows the most in the first two years. As babies grow their reflexes get better such as grasping and movement. Somethings in the body are replaceable, but others aren't (like the brain).
I don't think most people would be interested in this, but I would recommend it to people who are interested in science. It was a bit dry, but I did learn that the body needs food not only for growth but also to renew its cells.
Musfera in Esopus