Anatomically essential to seeing, photoreceptors are the nerve endings (brain cells called neurons) sensitive to light, that line the retina, located on the surface of the inner eyeball opposite the eye's lens. Here millions of photoreceptors are differentiated into the neurons called rods and cones, which are connected by the optic nerve to the brain. see thumbnail to leftIn this illustration, the rods and cones are the pink forms shown embedded in the anterior of the retina's surface. The more uniformly thin rods, among the more thickly formed cones.Also see afterimage, binocular vision, colorblind, cross-section, gestalt, night blindness or nyctalopia, Op Art, ophthalmology, optical, optical mixing, perception, and peripheral vision.