The majority of people around the world live in multilingual societies, and so it follows that plurilingualism should be considered normal. This book proposes a flexible and adaptive framework for designing and implementing language learning environments and tasks, which will be useful for practitioners working in classrooms where many languages are already spoken. The authors begin by presenting a state-of-the-art review of current research on language learning, language teaching and multilingual language acquisition. This is followed by a qualitative review of 37 multilingual research projects, which are treated as case studies to inform the practical guidance that constitutes the remainder of the book. The information and practical framework contained within this book will be of interest to researchers, teachers and teacher educators.