The article examines European institutions for implementing EU regulation. It assesses their development using seven different models that have been introduced or discussed for organising implementation. It argues that the development of European regulatory space has followed an evolutionary pattern involving gradual reshaping through a series of steps, with previous stages influencing later stages and institutions being built on existing structures. Despite pressures and frequent discussions of comprehensive change, existing organisations have managed to limit and shape reforms. The result has been institutional 'layering' and 'conversion' instead of streamlining, and a gradual strengthening of networks of national independent regulatory a...