More than 40 years experience with the EU decentralized agencies has made clear that the agencies are part and parcel of the EU’s institutional structure. These agencies can broadly be defined as bodies governed by European public law that are institutionally separate from the EU institutions, have their own legal personality, enjoy a certain degree of administrative and financial autonomy, and have clearly specified tasks. ‘Agencification’ of EU executive governance has thus become a fundamental feature of the EU’s institutional structure. Today there are around 40 EU decentralized agencies, which assist in the implementation of EU law and policy, provide scientific advice for both legislation and implementation, collect information, provide specific services, adopt binding acts and fulfil central roles in the coordination of national authorities. Agencies are part of a process of functional decentralization within the EU executive and operate in various policy fields, such as food and air safety, medicines, environment, telecommunications, disease prevention, border control, trademarks and banking, to name just a few.