This edited volume aims to contribute to the scholarship that has so far studied European youth in ethno-culturally and religio-politically divided separate clusters, such as “migrant-origin” and “native” youths. Accordingly, this introductory chapter lays the groundwork by arguing that European youth respond differently to the challenges posed by contemporary flows of globalisation, such as deindustrialisation, structural exclusion, and socio-economic, political, spatial, and psychological forms of deprivation and humiliation. Challenging the current uses of the term radicalism interchangeably with extremism, terrorism, fundamentalism, and violence, we take radicalism as a possible quest for the democratisation of democracies rather than a pathological issue. The novelty of this edited volume is to understand and explain the malaise of both native and immigrant origin youth simultaneously through a scientific method by de-culturalising and de-religionising what is socio-economic, political, and psychological in origin. So far, existing studies have focused on one or the other of these two phenomena, while this volume analyses them together.