This chapter sets the scene for the analysis of the external dimension of European agencies. Moreover, European Union (EU) agencies as global actors are introduced by means of an account of their international cooperation practice and relevant legal framework. European agencies could be situated arguably within the so-called 'executive branch' of the EU, where they seem to perform tasks of an administrative or technical nature. A feature common to most EU agencies is that they are entrusted with quite limited formal powers. The main novelty of the European Securities and Markets Authority (ESMA) decision, is the revival and, at the same time, the relaxation of the Meroni doctrine. The organisational design of the EU agencies gives an indication of how the bodies work and of the manner in which the interests of various relevant actors are represented in their decision-making and overall activities.