An Institute for an Empire is the first scholarly study of one of the world’s foremost scientific institutions, the Physikalisch-Technische Reichsanstalt (PTR) in Imperial Germany. The Reichsanstalt stood at the forefront of institutional innovation in science and technology during the late nineteenth and early twentieth centuries, uniting diverse practitioners and representatives of physics, technology, industry, and the state. It demonstrated how physics and industrial technology could help build a modem society and a modem nation-state. Moreover, it encouraged and helped inaugurate the era of Big Science. Professor Cahan also discusses the Reichsanstalt’s leaders and scientists, including Wemer von Siemens and Hermann von Helmholtz, as well as its scientific and technological work. Among the Reichsanstalt’s many accomplishments were contributions to the new quantum physics, development of physical standards and measuring instruments for science, industry, and the state, and testing work for a variety of German industries.