This article serves as an introduction to this special issue as well as a self-standing contribution. Using the lens of technology, we situate European integration (typically viewed as a political process) as an emergent outcome of a process of linking and delinking of infrastructures, as well as the circulation and appropriation of artefacts, systems and knowledge. These processes carried, shaped, flagged, and helped to maintain a sense of Europeanness, bringing out tensions in Europe and tensions about Europe. We call this 'hidden integration.' Yet the story of integration does not point to a seamless and inevitable process, a grand project with a set agenda. Instead it was a contested process throughout the 20th century leading to fragmentation as well as to integration. Our approach is contrasted with standard interpretations of European integration that treat European integration as an episode in international relations between nation-states.