The European Union (EU) consists of 27 European countries. It has evolved into a political community that not only deeply affects the daily lives of its citizens, but also plays an in-creasingly important role as an international actor beyond its borders. Reflecting the dy-namics of European integration since its inception, research on the EU in various disciplines has also flourished in the past decades. Given the unique structure of the EU as a political system beyond the nation-state, political scientists frequently use the EU as a "laboratory" for analysing and testing political science theories. This lecture course surveys the development and effect of European integration from a theoretical perspective and intro-duces students with a prior knowledge on the EU's political system into past and ongoing research on the EU. What can political scientists learn from the EU, and what can EU scholars learn from political scientists? The course will be divided in three parts. The first part reviews research explaining the development and evolution of European integration from the perspective of IR theories, classic integration theories and new critical approaches. Drawing on the comparative politics literature, public policy analysis and governance approaches, the second part surveys research on "the nature of the beast" which tries to capture what the EU actually is and how it can be accurately described. The last part brings together research on the effect of European integration both within and beyond the EU, such as the literature on Europeanization, diffusion and comparative regionalism. The goal of this lecture course is to critically assess the prospects and limits of using the EU as a case study in political science.