Cone

Cone cells in the eye are one of the two types of photoreceptor cells, which because of their shapes are called rods and cones. Rods are sensitive enough to respond to a single photon, the basic unit of light, but together they create only one coarse, gray image, which is adequate for seeing in poor light. Fine detail and color come from the cones, but they need a lot more light and work best in broad daylight. Inside the human eye, there are eighteen times more rods than cones. These are...