The eyeball has three layers: sclera, choroid, and retina.
Retina is the innermost layer of the eyeball (the third layer containing sensory receptors for sight), and composed of photoreceptor cells (rod cells and cone cells), neurons, and blood vessels.
The three layers of cells, from inside to outside are ganglion cells, bipolar cells and photoreceptor cells.
The two photoreceptor cells "rod cells and cone cells" in retina contain the light-sensitive proteins called the photopigments and stimulus light rays.
Rods are sensory receptors for dim light (scotopic vision); suited to night vision; but do not see color.
Cones require bright light; sensory receptors for bright light and color (photopic vision); sensitive to different wavelengths of light.
The entire retina has about 7 million cones and 150 million rods.
