E.N. Economou and the metal-to-insulator transition

In this paper, I interweave a brief history of the metal-to-insulator (MI) transition with a summary of E.N. Economou's related work. Those periods during which we overlapped are emphasized. I describe his activities as a graduate student at Chicago. A brief history of the MI transition follows, setting the stage for discussion of his pioneering contributions in the early 1970s to the theory of the localization of electrons, phonons, and photons in disordered materials; of his studies of the Mott–Hubbard transition; and of the work he did in the 1980s with his Exxon collaborators. After a few observations on the current state of our understanding of MI transitions, the paper concludes with a summary of Economou's contributions.