This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book presents key issues in communication research which have either been revisited or newly introduced. It provides an account of communication as a context-bound process, whose outcomes vary according to differences in the social contexts: child-peer v. child-parent, child-peer with the adult present v. absent, child-peer in symmetrical v. asymmetrical role relations, child-peer with same v. different partner. The book deals with three canonical key issues in communication research: imitation, intentionality and symbolic play. It demonstrates how imitation enhances co-ordination of activity and thus extends exchanges between toddlers. The book shows that, when related, immediate imitation and sensitivity to being imitated display three main features of a communicative system: codification, reciprocity and synchronism. It highlights the dialogical origin of semiotic activities, showing how dialogue-type interactions act as constitutive factors of new cognitive processes.