The human experience of vision involves three steps: (1) the transformation of a pattern of light to electrical impulses in the eyes, (2) the transmission of these electrical impulses from the eyes to the brain along the optic nerves, and (3) the decoding and assembly of these electrical impulses into visual sensations experienced in the brain. If any one of these three steps is significantly impaired, blindness results. In the vast majority of cases, blindness results from problems in the eyes and in the optic nerves, and not in the brain. In the few cases where blindness results from problems in the brain, the person usually regains some amount of vision due to brain plasticity Did cancer exist before man-made chemicals were around to create it?