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