The essays collected in this volume aim to provide the building-blocks of a learning-based understanding of the development of fundamental rights in the European Union. Instead of asking how much harmonization of fundamental rights is required at EU level or whether fundamental rights should rather be protected at domestic level, it acknowledges that even when it is desirable, harmonization may be in many cases politically unrealistic to achieve; that it may presume too much about our ability to identify how best to implement fundamental rights; and that the required legal bases may be missing. It also notes that we have currently no mechanism allowing us to identify, on a more or less systematic basis, the need for the Union to take action in this field. A learning-based understanding of the development of fundamental rights takes seriously these limitations which the fundamental rights policy of the EU is currently facing. This redefinition moues from substance to procedure: since there is uncertainty about how to improve the protection of fundamental rights (beyond the minimum requirement not to violate them), a fundamental rights policy should be about devising adequate mechanisms for the constant testing of the policies pursued in different settings, in order to arrive at a better understanding of how to best achieve their objectives. Reflexive governance, these essays argue, may represent one way of thinking about how to address this challenge. This hypothesis is tested in three policy areas: equality of treatment, data protection, and the establishment of an area of freedom, security and justice. The essays collected in this volume do not form a blueprint for the further improvement of the regime of fundamental rights protection in the EU