Brain grow abstract video. The brain is an organ in all vertebrate and most invertebrate animals that serves as the center of the nervous system. The brain is the most complex organ which interprets the senses, initiator of body movement, and controller of behavior. The brain is washed and protected by a fluid called cerebrospinal fluid. This fluid protects the brain from damage, removes waste products and provides the nutrients it needs to function properly. Royalty free stock videos from animation company Polymime Ltd.