The quantum-mechanical description of matter aims to explain how diverse properties of materials arise from the mutual interactions of many atomic nuclei and their associated electrons. While a more or less complete theory of ordinary electrical conduction in metals was developed in the early part of the twentieth century, newer phenomena such as high-temperature superconductivity and ballistic conduction in carbon-based electronic devices challenge our basic understanding of condensed-matter physics. It is an important goal to understand the subtle interactions leading to these phenomena, and if possible to control them. Can these inherently quantum-mechanical behaviors be extended to room temperature? If so, remarkable applications could be envisioned.