L.S. Vygotsky, the renowned Russian psychologist, argued that the true test of any scientific theory is not the contribution it makes to our understanding of the object of study but the extent to which it improves the concrete practical activities of people, including those that take place in educational settings. The fourteen original chapters included in the present volume document innovations in second and foreign language teaching that are rooted in Vygotsky’s theory of cognitive development. Researchers and language teaching practitioners will find implementations at the classroom and programmatic levels of Vygotskian principles and concepts, including cognitive mediation, the zone of proximal development, activity theory, internalization, verbalization, and materialization.