Retina. Coloured scanning electron micrograph SEM of a longitudinal section through the retina. This is the multi_layered light sensitive layer at the back of the eye, which transmits light to the optic nerve. Light enters the retina from the top of the image. The layers are: gang_ lion cells red, at top, inner plexiform layer brown granular layer, bipolar cell layer brown, outer plexiform layer of nerve synapses yellow, cell bodies of rods and cones blue, and rods and cones red, the specialized light sensitive cells photoreceptors. Rods detect light intensity and cones detect colour. The pigment layer is not seen off image at bottom.