This book pioneers the study of bilingualism across the lifespan and in all its diverse forms. In framing the newest research within a lifespan perspective, the editors highlight the importance of considering an individual's age in researching how bilingualism affects language acquisition and cognitive development. A key theme is the variability among bilinguals, which may be due to a host of individual and sociocultural factors, including the degree to which bilingualism is valued within a particular context. Thus, this book is a call for language researchers, psychologists, and educators to pursue a better understanding of bilingualism in our increasingly global society.