This book gives an overview of the linguistic development of Korean-English bilingual children living in the US. It provides a detailed longitudinal account of English and Korean acquisition in early childhood, offering a close examination of Korean-American children's code-switching and morphology and syntax development during a time when their language dominance is shifting rapidly. The book sheds light on the broad and creative linguistic capabilities of bilingual children, expands our understanding of heritage language acquisition and furthers bilingualism research on typologically distinct language pairings. Researchers investigating heritage language development in early childhood will find the extensive longitudinal data a rich source of comparison and the book will be a useful resource for scholars and graduate students interested in sequential bilingualism, second language acquisition and heritage speakers.