The chapter introduces the book, Solidarity in EU Law: Legal Principle in the Making, highlighting the political, social and human rights background against which the concept of solidarity is gaining a more substantial role in shaping the European Union's legal order. It places the summarised book chapters in this context, serving as a point of reference to reflect upon the tribulations that European solidarity is likely to face in the future, including the aftermath of Brexit and challenges to the rule of law in the EU.