Lutein and zeaxanthin are members of the carotenoid family, a family best known for another one of its members, carotene (see Beta-Carotene). They are natural fat-soluble yellowish pigments found in some plants, algae and photo-synthetic bacteria. They serve as accessory light-gathering pigments and to protect these organism against the toxic effects of ultra-violet radiation and oxygen. They also appear to protect humans against phototoxic damage. Lutein and zeaxanthin are found in the macula of the human retina, as well as the human crystalline lens. They are thought to play a role in protection against age-related macular degeneration and age-related cataract formation. They also be protective against some forms of cancer. This two carotenoids are sometimes referred to as macular yellow, retinal carotenoids or macular pigment.