Rhodopsin (also known as visual purple) is a light-sensitive receptor protein involved in visual phototransduction. It is named after ancient Greek ῥόδον (rhódon) for rose, due to its pinkish color, and ὄψις (ópsis) for sight. Rhodopsin is a biological pigment found in the rods of the retina and is a G-protein-coupled receptor (GPCR). It belongs to a group of photoswitchable opsins. Rhodopsin is extremely sensitive to light, and thus enables vision in low-light conditions. When rhodopsin is exposed to light, it immediately photobleaches. In humans, it is regenerated fully in about 30 minutes, after which rods are more sensitive. Rhodopsin was discovered by Franz Christian Boll in 1876.