The cerebrum consists of the left and right hemispheres, which is how the brain is often depicted to the public. The cerebellum sits at the base of the brain near the brain stem. The cerebrum also houses five out of five of the major areas of the brain. The frontal lobe is the last portion of the brain that fully develops and is not fully “grown” until after a person passes from adolescence into adulthood. This portion of the brain is also the largest.