Digitally linked media can be understood as a conglomerate of cooperative tools, platforms, and infrastructures. In the course of digitalization, the regulation and design of technical and media infrastructures has given rise to numerous public controversies as well as institutional negotiation processes and will continue to do so. On the one hand, infrastructures elicit public debates within societies about their design, while on the other hand, the actual configuration of digital and media infrastructures, i.e. the ‘infrastructuring’, usually occurs out of reach of public perception, within organizations or committees of standardization. Infrastructures often subside into a deceptive invisibility from which they are only raised into the spotlight by maintenance or repair work or noticeable malfunction. With the progressive digitalization particularly of information technology, (media) infrastructures permeate ever more societal domains. Systems of societal functioning were and are permanently configured and reconfigured by media infrastructures. At the same time, infrastructures change the media practices of people and are in turn changed by them. Section A of the cooperative research center ‘Media of Cooperation’ and its projects foreground the ‘infrastructuring’ of media infrastructures in its various dimensions. The projects firstly address variable modes of scaling―from networks within hospitals up to national ISDN-networks―; secondly, different states of operating―from online/offline to interruptions of service―; and thirdly, the three elements of cooperative tools, platforms, and infrastructures.