This volume exemplifies the general theory of a field of professionals of security (in the line of our first book Illiberal Practices of Liberal Regimes) and proposes a map of die European internal security agencies (Europol, Eurojust, Frontex, OLAF). It insists on the relations between the agencies in order to give a better idea of the flow of communication and strategic or operational decisions produced at the EU level as too often die audience has only monographers about these agencies. Any researcher, student, NGO or policy maker interested in security in the EU will thus have a better idea of the relations between die agencies and a greater understanding of what is at stake with liberty, security and justice in Europe.