Vladimir Prelog (1906 – 1998) was awarded half of the 1975 Nobel Prize in Chemistry for his research into the stereochemistry – the study of the relative spatial arrangements of atoms -- of organic molecules and reactions. Prelog performed wide-ranging research on the stereochemistry of alkaloids, antibiotics, enzymes, and other natural compounds. In particular, he contributed to the understanding of stereoisomerism, in which two compounds of identical chemical composition have different, mirror-image configurations. With Robert Cahn and Sir Christopher Ingold, he developed a nomenclature for describing complex organic compounds. This system, known as the Cahn-Ingold-Prelog (CIP) system, provided a standard and international language for precisely specifying a compound's structure.