The Nobel Prize in Chemistry 1938 was awarded to Richard Kuhn "for his work on carotenoids and vitamins".
 

Richard Kuhn received his Nobel Prize one year later, in 1939. During the selection process in 1938, the Nobel Committee for Chemistry decided that none of the year's nominations met the criteria as outlined in the will of Alfred Nobel. According to the Nobel Foundation's statutes, the Nobel Prize can in such a case be reserved until the following year, and this statute was then applied. Richard Kuhn therefore received his Nobel Prize for 1938 one year later, in 1939. Richard Kuhn was caused by the authorities of his country to decline the award, but he later received the diploma and the medal.
 

Richard Kuhn was fascinated by a class of organic compounds called polyenes, on account of their distinctive long chains of carbon atoms linked by alternating double and single bonds. The fact that several vitamins are also members of the carotenoid family led Kuhn to shift his focus once again. His first major breakthrough in this field came in clarifying Paul Karrer's early results concerning the structural formula of beta-carotene, the precursor of vitamin A.