This introduction presensts an overview of the key concepts discussed in the subsequent chapters of this book. The book pursues two ambitious aims, the development theory that shows how communication and learning are interlinked, mutually constituting and defining of each other in a closely integrated domain of meaning making. It proposes a framework in which all means for making meaning become visible and recognizable, a framework that gives recognition to agency, and to identity, to ways of knowing and to learning of all kinds, everywhere. It begins the task of making what is currently unnoticeable noticeable, what is inaudible audible and what is invisible visible. In other words, one sets out a theory that encompasses, marks out and accounts for a large field of social semiotic practice; at the same time, to introduce tools that the theory produces and that serve to provide descriptions, integrated analyses and insights for this field.