To understand how information produced by European agencies contributes to the convergence of individual state policies it is often necessary to study the venues where experts, policy makers, representatives of interest groups or civil society, etc., socialize. In particular, it is argued that those venues and arenas are key settings where social learning process takes place. It is not as common, however, to study the conditions under and the processes by which information is generated within/by those agencies. This type of analysis could nevertheless be of interest for better understanding the elementary mechanisms that compose socialisation and social learning processes : by analysing the actual production process of information, one can disclose what are the peculiar nature and features of this information and according to which it is considered as true, reliable or legitimate by actors evolving in European arenas, networks and institutions. It helps explaining the efficacy of ideas, i.e. their capacity to circulate, to convince and, finally, to affect the behaviours of its main targets.