Superconductivity—the loss of resistance in various materials close to absolute zero temperature—was a hot topic after World War II. Advances in nuclear reactor technology led to the discovery of the isotope effect in 1950 (Maxwell 1950; Reynolds et al. 1950), which brought about crucial insights about the role of electron-lattice interactions in superconductors that ultimately led to the formulation of a microscopic theory of this phenomenon. Generations of physicists had been struggling to find an explanation of superconductivity ever since its discovery in 1911 by Heike Kamerlingh Onnes.