Color enhanced scanning electron micrograph (SEM) of rods and cones in the human retina. The retina is the back part of the eye that contains rods and cones, photoreceptor cells that respond to light and color. The rods are sensitive to changes in light, shape, and movement. In a dim room, we use mainly our rods. The cones are not as sensitive to light as the rods but are sensitive to one of three different colors (green, red or blue). Signals from the cones are translated by the brain into the perception of color.