This book was first published in French in 1994. It has been a training support to numerous researchers as well as practitioners, such as teachers, health workers, personal or sport trainers. Since then, it has constantly been republished and a glossary has been added in 1998. This version is the first complete edition of the book in English. The main idea of this new interview technique is to help a teacher, a supervisor or a researcher to guide the student, the practitioner or the subject to give a fine retrospective description of an action. As it is only the subject that has access to this mental or physical action, the goal is to help the subject with the verbalization, putting the implicit knowledge of this action in words. Yet, to achieve this verbalization, we need guidance, because we don't know how to give such a description ourselves. If we leave the interviewee without guidance, he risks remaining in the implicit, speaking in a general way, or in an incomplete or imprecise way, commenting instead of describing. The explicit and precise description we aim is the opposite of the implicit, meaning a fine, detailed and complete way of putting the action in words. The final aim is to elucidate what the subject did to seek his goal