Wireless communications, perpetually a source of innovation, is entering new and uncharted territory. In order to enhance system performance and cater for the services and applications of the future, there is the need for cooperative and cognitive communications paradigms that support advanced coexistence technologies for radio optimization. In short, wireless communications is moving towards a disruptive phase, where the speed and capability of interdisciplinary knowledge integration, for systems cooperation and coexistence, becomes a requirement for survival. This needs new thinking, and the development of architectures and facilitators for novel flexible radio technologies. To account for this paradigm shift and position Europe to benefit most from it, experts in areas of cooperation and coexistence, comprising but not limited to realms such as cognitive radio, cognitive networking and flexible networking, must integrate and harmonize their agendas. Through this approach, to paraphrase a common adage, "the whole will become stronger than the sum of the parts". Moreover, there is the need to produce a next generation of European researchers, with the right skills-sets to solve the challenges of optimisation for cooperative and coexisting wireless systems. The ACROPOLIS NoE is specifically designed to meet these challenges; it has a strong, interdisciplinary, joint-research agenda, fostering rapid innovation that is of the highest quality and is able to bridge the gaps in European research. Its structure allows it to react rapidly to changes in the research landscape, where integration of research activities to achieve critical mass, and spreading of excellence throughout industry, other research organisations and elsewhere, are at the very heart of its formulation and ideals. To summarise, ACROPOLIS fosters relevant European excellence in research and education, and through the amalgamation of this strives to achieve new heights that would otherwise be impossible.