This book is about network infrastructures. We consider network infrastructures as socio-technological systems characterized by the interdependence and complementarity of two dimensions: institutions and technology. Relying on a combination of nodes and links, these infrastructures require coordination along both dimensions in order to fulfill functions identified as “critical.” Critical functions determine the capacity of a network to deliver expected services in line with societal values. Thus understood, network infrastructures cover a wide range of sectors, from energy, water and sanitation, urban transportation, to telecoms and the internet. These networks provide the backbone of economic as well as social activities. The key argument underlying our analysis is that alignment between the two dimensions, institutions and technology, is central to the fulfillment of the performance expected from these networks. Misalignment can generate discrepancies or gaps challenging the integrity of a network and its capacity to meet its goal. This introduction posits our core hypotheses and concepts, and draws a general picture of the theoretical as well as empirical content developed in the coming chapters.