Chapter 7 turns to the question of diversity from a health perspective, with a focus on scientific uncertainty and regulatory experimentation. This is about the effectiveness of EU intervention, the ability of the EU, as a functionally driven risk regulator, to select the best health intervention, in terms of reduced mortality and morbidity. It investigates how the principle of precaution is used by the Court to grant a certain leeway to the national and the EU legislature. Notably, the principle is applied not only to uncertainty about the existence of health risks, but also to uncertainty about the effects of policy interventions. The chapter then examines two legal devices designed to preserve the regulatory autonomy of Member States: subsidiarity and minimum harmonisation. Through three case studies – tobacco plain packaging, the ban on tobacco for oral use and front-of-pack nutrition labelling – the chapter highlights the contradiction between the need for regulatory diversity and the need for market uniformity, and the resultant tensions with the principles of conferral and subsidiarity.