"This chapter presents the reasons why the edited volume seeks to determine the extent to which and in which domains we are now confronted with a 'new ECB'. It also presents the various perspectives one can take in characterising the ECB's transformation, the main elements in the evolution of the ECB, and the main causes, triggers and factors in the ECB's evolution. The chapter discusses the essence of the evolution of the ECB by looking at a few elements that stand out. These elements relate to the main features of the ECB enshrined in the Treaties, namely: 1) the ECB's substantive mandate, to which definition Article 127 TFEU is central; 2) the ECB's relationship to euro area Member States' sovereign debt, in which respect Article 123 TFEU is central; and 3) the ECB's relationship to politics, for which Article 130 TFEU is central. The chapter, moreover, discusses several possible causes, triggers and factors for the ECB's evolution. It evidences that the emergence of a 'new ECB' is not so much a consequence of Treaty change or a change in the underlying ideas, but is very much a reaction to the events that have occurred since the creation of the ECB, and is determined by autonomous action by an ECB, which has used the gaps inherent in its mandate, and by political decision making. Finally, the chapter highlights some of the areas where relevant developments can be expected, and some of the main challenges the ECB will need to address"-- Provided by publisher.