In this accessible introduction to Vygotskian sociocultural theory, narratives illuminate key concepts of the theory. These key concepts include mediation; Zone of Proximal Development; collaborative dialogue and private speech; everyday and scientific concepts; the interrelatedness of cognition and emotion; activity theory; and assessment. A final chapter provides readers with an opportunity to consider two additional narratives and apply the SCT concepts that they have become familiar with. We hear from learners, teachers and researchers in a variety of languages, contexts, ages and proficiencies. Intended for graduate and undergraduate audiences, this new edition of the textbook includes controversies in the field, improved questions for collaborative discussion and provides updated references to important work in the literature of second language teaching, learning and research.