Adolf Otto Reinhold Windaus (; 25 December 1876 – 9 June 1959) was a German chemist who won a Nobel Prize in Chemistry in 1928 for his work on sterols and their relation to vitamins. He was the doctoral advisor of Adolf Butenandt who also won a Nobel Prize in Chemistry in 1939. Biography He was born in Berlin, Germany on 25 December 1876 to a family who owned a drapery business. He attended a prestigious French grammar school, where he focused primarily on literature. Windaus began studying medicine at the University of Berlin in about 1895 then proceeded to study chemistry at the University of Freiburg. He married Elizabeth Resau in 1915 and they had three children together, Günter, Gustav, and Margarete. After earning his PhD in medicine, Windaus became the head of the chemical institute at the University of Göttingen from 1915 to 1944. Throughout his life, Windaus won many awards including the Goethe Medal, the Pasteur Medal, and the Nobel Prize for Chemistry. In addition to his many accomplishments and discoveries in science, Windaus was also one of the very few German chemists who did not work with the Nazis and openly opposed their regime. As the head of the chemical institute at the University of Göttingen, Windaus personally defended one of his Jewish graduate students from dismissal. Windaus believed that while every man had a moral code, his science was motivated by curiosity, and was not driven by politics, ethics, and applications of his discoveries. This viewpoint caused Windaus to decline to research poison gas during World War I. Research He was involved in the discovery of the transformation of cholesterol through several steps to vitamin D3 (Cholecalciferol). He gave his patents to Merck and Bayer and they brought out the medical Vigantol in 1927. Sterols Windaus began his research by studying sterols. In particular, Windaus studied cholesterol, which is the best known sterol. Sterols are nitrogen-free secondary alcohols with high molecular weight that contain alicylic systems, or hydrocarbon rings. Cholesterol was first discovered in human gallstones and is a mono-unsaturated alcohol found in all higher animals, both as a free alcohol and fatty acid ester. Windaus was fascinated by how cholesterol levels in the body fluctuate, in particular how it increases during pregnancy and decreases during disease. He researched sterols in insects, echinodermata, and sponges, called zoosterols. Many of these zoosterols have the same formula