Hans Karl August Simon von Euler-Chelpin (15 February 1873 – 6 November 1964) was a German-born Swedish biochemist. He won the Nobel Prize in Chemistry in 1929 with Arthur Harden for their investigations on the fermentation of sugar and enzymes. He was a professor of general and organic chemistry at Stockholm University (1906–1941) and the director of its Institute for organic-chemical research (1938–1948). Euler-Chelpin was distantly related to Leonhard Euler. He married chemist Astrid Cleve, the daughter of the Uppsala chemist Per Teodor Cleve. In 1970, their son Ulf von Euler, was awarded the Nobel Prize in Physiology or Medicine. Personal life von Euler-Chelpin was born on 15 February 1873 at Augsburg, Germany to Rigas Georg Sebastian von Euler-Chelpin and Gabriele von Euler-Chelpin (née Furtner). His father was a captain in the Royal Bavarian Regiment, who was soon transferred to Munich. During his childhood, he spent most of his time with his grandmother at Wasserburg am Inn. He went to the Royal Junior High School in Augsburg (predecessor of Holbein Gymnasium ), also in Würzburg and Ulm. After serving as a one-year volunteer in the Bavarian first Field Artillery Regiment, he took interest in the color theory and began studying art at the Munich Academy of Painting (1891–1893). He was taught under Schmid-Reutte and Lenbach, a German painter of realist style. He thereafter went to attend the University of Berlin to study chemistry under Emil Fischer and A. Rosenheim, and physics under E. Warburg and Max Planck; where in 1895 he received his doctorate. In 1899 von Euler-Chelpin was appointed to teach as Privatdozent in the Royal University at Stockholm where he began visiting the laboratory of van 't Hoff, one of the many who influenced Euler-Chelpin's interest in science along with Nernst. In 1902 he took Swedish citizenship. Nevertheless, during the First World War, von Euler-Chelpin took part in voluntary service in the German Air Force. During the Second World War, he worked in a diplomatic mission on the German side. In 1906 he was appointed Professor of General and Organic Chemistry in the Royal University, Stockholm. In 1929, the Knut and Alice Wallenberg Foundation and the International Education Board of the Rockefeller Foundation established in Stockholm the Vitamin Institute and Institute of Biochemistry, and Euler-Chelpin was appointed as its director. In 1941 he retired from teaching, but continued his research. Hans von Euler-Chelpin married twice. His first wife