Photoreceptors in the retina take in light and spit out electrical signals that the brain interprets. The two main types of photoreceptors, rods and cones, have different jobs in this process. Concentrated near the center of the retina, the cones — the larger, sparser cells in this image — process color. The smaller rods are responsible for low-light vision. In dim light, it’s very difficult to distinguish colors, because the rods are doing the heavy lifting. The human retina has around 100 million rods and only about six million cones. But don’t let that disparity convince you to become nocturnal — animals like owls that are active at night have even more rods (and fewer cones) packed into their retinas, so hunting in the dark is a relative breeze.
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