This special issue stresses the importance of material culture in diplomatic studies of science and technology. In our studies, objects are considered powerful tokens of complexity in diplomatic encounters and of asymmetry in international relations. The contributors are committed to theorizing about the role of objects in diplomatic exchanges during the postwar period and, at the same time, the role of diplomacy in constituting the materiality of nuclear things. Our approach combines attention to the political and diplomatic nuclear history with recognition of the roles played by nuclear artifacts throughout the whole spectrum of diplomatic activities. On the whole, we argue that the material approach should be located at the center of the study of nuclear history and the diplomatic exchanges that made it possible.