This special issue explores the power that images with a techno-scientific content can have in international relations. As we introduce the articles in the collection, we highlight how the study of this influence extends current research in the separate (but increasingly interacting) domains of history of science and technology, and political science. We then show how images of different types (photographs, cartoons and plots) can inform inter-state transactions through their public appeal alongside the better-studied dialogic practices of the diplomatic arena. (...) Finally, we offer an analysis of the interlacing of different diplomatic tracks based on words and images and conclude that, in contrast with words, images conflate agency and argument, therefore creating opportunities to inform transactions and negotiations which their designers may not have even intended. (shrink)