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).