Infrastructures have become more and more critical to the functioning of society, as economic and social processes to a large extent rely on the services provided by such systems. Failure of these infrastructures, therefore, is one of the most important vulnerabilities of modern society. In addition and simultaneously much change is taking place within and around these infrastructures. This change includes: increasingly rapid technological change, rapid institutional change, increasing system complexity, increasing trans-boundary dependencies, tensions between market concerns addressing (short-term) economic gains and increasing demands on service quality. These and other changes pose formidable challenges to policy makers, business innovators, system designers, infrastructure operators and scientists alike. Critical Infrastructures: State of the Art in Research and Application , comprising a selection of reviewed and edited contributions from all over the world, aims to shed light on the various aspects of critical infrastructures.