Slim Rods and Fat Cones The rods and cones in the retina are the sensory receptors for vision. They convert light into electrical impulses that are ultimately transmitted to the brain. Color has been added to this scanning electromicrograph to clearly distinguish the rods and cones. The rods, colored green, are long, thin, and more numerous than the cones, colored blue, which are tapered at one end and shorter and fatter than the rods. As the photo shows, the rods and cones are densely packed in the retina, with many rods surrounding a few cones.
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