This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book describes some of Klein's and Bion's basic ideas and to show how they are used and are being developed in everyday clinical work by several analysts. It devoted to the work of Melanie Klein. The particular lectures published here were not meant to give a comprehensive view of Klein's or Bion's works, but instead were intended to present some of their more interesting and important ideas in a clinically alive way to those relatively unfamiliar with them. The emphasis therefore has been to show how the ideas and theories are used in practice by analysts working now. The lectures show how some of Klein's original ideas are used today in much the same way as she used them, while others have been developed and modified- evidence that psychoanalysis is, as it should be, a living science and method of treatment.