False-colour scanning electron micrograph (SEM) of the eye retina. The retina, which detects visible images, is made up of many layers of cells (seen here). Running diagonally from top left (purple) is a layer of closely-packed rod cells. Rod cells and cone cells (not visible here) are specialized light sensitive cells. Rods detect light intensity & cones detect colour. Nerve cells beneath this (white, brown) transmit nerve impulses from rods & cones to the optic nerve & brain. At top right, a layer of pigment cells which is normally attached to the surface of rods & cones, has peeled away. Magnification: x720 at 6x7cm size. Magnification: x1100 at 4x5 inches size.