Content and Language Integrated Learning (CLIL) is an established approach to support multilingualism in Europe by teaching various school subjects in an additional language. The practices used, however, vary considerably. Our book considers this diversity by looking at CLIL scenarios, defined as learning environments supporting content learning, language learning and skill development in task-based learning settings, with a strong focus on interaction in different curricular contexts (primary and secondary school and CLIL teacher education at university) and at various levels of proficiency (primary, secondary, tertiary). CLIL by Interaction is understood here both as negotiation of meaning and form as well as discourse to empower CLIL learners to participate in social interaction. Contents include: (1) Language Education Policy and CLIL Principles (Rita Kupetz, and Alexander Woltin); (2) Peer-to-Peer Scaffolding in a Primary Science Class (Carmen Becker); (3) Empowering the Prospective CLIL Teacher through the Analysis of Classroom Interaction (Maxi Kupetz, and Rita Kupetz); (4) Interactive and Collaborative Supports for CLIL: Towards a Formal Model Based on Digital Literacy (Ivana Marenzi); and (5) Approaching Content through Communicative Interaction (Jana Roos).