This new volume of work highlights the distinctiveness of child SLA through a collection of different types of empirical research specific to younger learners. Characteristics of children's cognitive, emotional, and social development distinguish their experiences from those of adult L2 learners, creating intriguing issues for SLA research, and also raising important practical questions regarding effective pedagogical techniques for learners of different ages. While child SLA is often typically thought of as simple (and often enjoyable and universally effortless), in other words, as "child's play", the complex portraits of young second language learners which emerge in the 16 papers collected in this book invite the reader to reconsider the reality for many younger learners. Chapters by internationally renowned authors together with reports by emerging researchers describe second and foreign language learning by children ranging from pre-schoolers to young adolescents, in home and school contexts, with caregivers, peers, and teachers as interlocutors.