Emergent quantum materials. The properties of quantum materials are principally defined by quantum mechanical effects at macroscopic length scales. These materials exhibit phenomena and functionalities not expected from classical physics. While quantum materials has been a topical area of modern materials science for decades, today it is at the center stage of technologies ranging from electronics, photonics, energy, defense, and sensing to environmental and biomedical applications, and, in particular, quantum information science and technology. This issue of MRS Bulletin presents important developments in emergent quantum materials at the intersection of materials science and condensedmatter physics. The cover provides a schematic view of monolayer CuO2 fi lms on a Bi-2212 substrate. See the technical theme that begins on p. 340.