Isidor Isaac Rabi (1898-1988) was born in Rymanow, Poland, at that time part of the Austro-Hungarian Empire, and immigrated with his family to the United States in the first year of his life. After earning a Ph.D. in physics at Columbia University, he went to Europe, where the twin revolutions of relativity and quantum mechanics were transforming our understanding of the universe. In Europe, he studied and worked alongside Erwin Schrödinger, Niels Bohr, Werner Heisenberg and the other titans of modern physics. Returning to the United States, he took up a professorship at Columbia, where he was to remain for most of his career, training successive generations of scientists. In 1944 he was awarded the Nobel Prize in Physics for his application of the resonance method to the measurement of the magnetic properties of atomic nuclei. His discoveries were fundamental to the development of magnetic resonance imaging (MRI) for internal medicine and to the creation of the laser and atomic clock. During World War II, he directed the Radiation Laboratory in Cambridge, Massachusetts, refining radar technology. As a visiting consultant with the Manhattan Project, he witnessed the detonation of the first atom bomb. After the war, he served as science advisor to President Truman, and was one of the founders of the Brookhaven National Laboratory and of the European Centre for Nuclear Research (CERN). As Chairman of the Columbia Physics Department, he oversaw the work of distinguished physicists such as Charles Townes and Leon Lederman. A beloved figure in the world of science, he received numerous awards for his commitment to the peaceful uses of atomic energy.