As succinctly summarized by Wolf, 1 lack of vitamin A (all-trans-retinol) was recognized by ancient Egyptians as causing a visual deficiency involving the retina and cornea that could be cured by eating liver. One of the symptoms of vitamin A deficiency is night blindness or nyctalopia (from Greek νύκτ-, nykt− night; and αλαός, alaos− blindness), recognized by ancient Greeks, including Hippocrates, as affecting the retina. 2 In 1913 McCollum showed that “fat-soluble factor A” was essential for growth of a rat colony (reviewed in ref 3). The treatment of factor A-deficiency included liver or liver extracts, but later in 1930 Moore found that yellow pigment (carotene) was a good substitute for this therapy. 4 A major breakthrough occurred in 1931 when the chemical structures for β, β-carotene and retinol (its all-trans isomer now known as vitamin A) were determined by Karrer and colleagues. 5 But, it was Wald who discovered that retinol derivatives constitute the chemical basis of our vision, 6 a contribution subsequently recognized by a Nobel Prize award in 1967. In 1950− 1960, a variety of vitamin A metabolic