The brain is not fully developed until a person is about 25 years old. The executive office in the front part of the brain, known as the prefrontal cortex or the frontal lobe, controls problem solving, emotion regulation, impulse control, planning, and decision making. This suite of skills and controls expands from adolescence through adulthood. The grey matter that reflects a healthy brain increases in totality over time, but also decreases at certain times, such as during puberty. The brain “prunes” the brain’s pathways, so that messages are delivered more efficiently. It is as if the brain is a rapidly growing garden, with blooming plants as well as weeds.