This book analyses the recent development and challenges in the evolving constitutionalism of the European area as it has been developed by interaction of the European Court of Human Rights and the Court of Justice of the European Union. It publishes the result of several competitive research projects in which have participated some of the most representative European constitutionalists, which have studied the different issues arising from the overlapping legal orders that need to coexist and are, ultimately, interpreted by an autonomous supranational court. In a nutshell, it deals with the main aspects of the European constitutional issues taking into account the perspectives of both European «Constitutional» Courts: the European Court of Human Rights and the Court of Justice of the European Union.