The first chapter of the book introduces the reader to the study of Europeanisation in teacher education and provides some main information about the theoretical framework and the way that the study was carried out. After an initial discussion of the study's relevance and research questions, there will be a conceptual clarification of the term Europeanisation drawing on the literature of European integration theories. In policy areas, such as teacher education, Europeanisation takes the form of a policy learning process that can have diverse effects on national systems. To explore this process, the chapter presents a stage matrix for analysing the policy change and conceptualises teacher education as a policy ecosystem with multiple interacting layers (i.e. global, European, national, institutional), shaped by the dynamics of Europeanisation. A comparative case study is selected as an appropriate research design that attends simultaneously to the macro-, meso-, and micro-dimensions of the teacher education ecosystem.