Content and Language Integrated Learning has received a strong tailwind in European educational and language policies. It is on the verge of becoming a mainstream phenomenon. However, an overly speedy implementation of «CLIL for all» might bear a number of risks for all groups of stakeholders. The purpose of this book is to link the growing empirical knowledge about the full complexity of CLIL to the current European educational and language policies. The articles collected in this volume contribute to a more systematic evidence base of CLIL that has frequently been called for at a European level. This bi-lingual volume (English/German) brings together authors from several European countries to present significant findings from recent CLIL research in the light of the developments in education policy. The four parts of the book focus on the reconstruction of learning processes, learner achievement, theory-driven investigations of the concept of CLIL itself, and critical reflections on the current «CLIL boom».