The Maastricht Treaty (the “Treaty”) first introduced the status of EU citizenship. The twentieth anniversary of the signing of the Treaty, marked in 2013, was declared the European Year of the Citizen. Union citizenship has been understood as the world’s first post-national citizenship, although it is still complementary to national citizenships. EU citizens enjoy rights that have been expanded, modified, and reinterpreted in light of the EU integration process. The Court of Justice of the European Union (CJEU) has been a driving force in this process. This twentieth anniversary has provided the occasio for this special issue. Indeed, much has happened over the last two decades. The Maastricht Treaty entered into force on the heels of German reunification, and afterwards, a series of EU treaties followed: The Amsterdam Treaty, the Nice Charter of Fundamental Rights, the aborted constitutionalization process and the Rome Treaty in 2004, and the Treaty of Lisbon. The Euro took over former national currencies in 2002; the enlargement process led to today’s twenty-eight Member States. But the ratio of this special issue is based on other events as linked to the 2008 financial crisis, bailouts, the fiscal compact, and similar measures. In a nutshell, the timeliness of this volume is linked to the current financial disarray. Since prognosis presupposes diagnosis, no further words are necessary as to the importance of this task. It is (almost) self-evident that before taking action and preparing for the future, one needs to address the very first question: Nosce te ipsum or know thyself. Union citizens need to take a step back and ask what they need to be and who they want to become.