Healthy brain. Coloured three-dimensional magnetic resonance imaging (MRI) scan of a healthy human brain seen from the front. The front of the brain is at top. The cerebrum, the largest part of the brain, consists of four lobes of which two, the frontal (dark pink) and temporal (yellow), are visible here. The cerebrum, which controls conscious brain activity, is folded into gyri and fissured with sulci. The cerebellum (green) and brainstem (pink) subconsciously control the body's vital functions. MRI scanners build images of the human body using pulses of radio waves. The slices" are compiled into a three-dimensional image by computer."