Differentiation has become the new normal in the European Union (EU) and one of the most crucial matters in defining its future. In broad terms, it can be defined as a tool to accommodate diversity in the EU, whether through major long–term projects like EMU or as a flexible means to cope with crises and political divergence. This definition allows for a multi-dimensional and innovative approach that accounts for different models (integration, cooperation), different dimensions (horizontal/vertical, internal/external), and different actors (EU Member States, non-EU countries, sub-national actors) of differentiation. Depending on the form it takes and how it relates to the overarching institutional and political system of the EU, differentiation can lead to the progressive convergence and integration or further political fragmentation, within and outside the EU. In this lecture, Nicoletta Pirozzi will try to uncover and assess both opportunities and risks of differentiation for the future of Europe, by evaluating its impact on the effectiveness, accountability and sustainability of EU governance. In doing so, Pirozzi will benefit from the preliminary results of the Horizon 2020 project EU IDEA – Integration and Differentiation for Effectiveness and Accountability (https://euidea.eu). In particular, she will address differentiation both as a policy practice and a policy choice and take into account its implementation in different policy sectors – from economic governance to security and defense to migration and asylum.