Prigogine, Ilya (prĭgˈəjēn) [key], 1917–2003, Belgian chemist, b. Moscow. He was raised and educated in Belgium, receiving his doctorate in 1941 and joining the faculty of the Free Univ. of Brussels in 1947. In 1959 he became director of the International Solvay Institutes in Brussels, a position he held until his death. He also founded and served as director (1967–2003) of what is now the Ilya Prigogine Center for Studies in Statistical Mechanics and Complex Systems at the Univ. of Texas at Austin. For his development of mathematical models of irreversible thermodynamics (as opposed to the classical reversible systems), he was awarded the 1977 Nobel Prize in Chemistry. Prigogine's work was important in the development of the field of complexity.