Cecily O\'Neill has had a formative impact on the evolution of the creative and dynamic mode of teaching called process drama. Process drama characterises work powered by transformatory outcomes that bring together drama education and theatre practice. Dorothy Heathcote and Gavin Bolton were perceived as the pioneers of a new and radical form of educational praxis, but it was O\'Neill who made that praxis accessible to educators worldwide. Her work on structuring classroom drama, her writings on pretext and process drama, her studies on the imagination, multicultural education, and dramatic form have been influential throughout the UK and Europe, North America and Australasia. This book is a compilation of the formative articles of O\'Neill along with significant commentaries from leaders in the field. It is informed by her work but it is not simply about her. The book explores central questions about imagination: why is it critical to process drama? And how should leaders of process drama promote imagination in their work? It will be of immense value to drama practitioners and teacher trainers.