High protein foods are very important for gaining muscle, but carbohydrates and fats are also necessary sources of energy. If your goal is to gain lean muscle, you should focus on exercising regularly and eating more calories each day from muscle building foods.

At birth, the average baby's brain is about a quarter of the size of the average adult brain. Incredibly, it doubles in size in the first year. It keeps growing to about 80% of adult size by age 3 and 90% – nearly full grown – by age 5. The brain is the command center of the human body.