Studying the EU requires to take into consideration a political system which has acquired a certain normality but which is also able to confront crises. To cope with this challenge, we have decided to bring together a range of excellent scholars from different Member States and different disciplines and academic traditions. A Companion must absolutely avoid any form of ‘clannism’ to offer readers, especially undergraduate and graduate students, a collection of concise and well-documented and well-written chapters that can be read independently of each other. A bit like what used to be called in the past an encyclopaedia, our objective is to propose chapters that do not necessarily aim to develop one specific research hypothesis, but seek to be very informative with bibliographical references helping go further on every topic related to the European Union. This Companion is an invitation to reflect on EU politics beyond the nation-state while not falling into the illusion that the nation-state has lost all its power and legitimacy. Desires to return to an exclusive nation state exist among citizens, as the Brexit experience has demonstrated, but there are also desires to join the European Union in order to better face the world, as Ukraine’s application for membership following Russia’s military intervention has shown. These contradictions in citizens’ expectations need to be observed, compared and understood as they show that uniformity is hardly the model that governs the European Union.