This introductory chapter presents the main topics and orientations of the book. Its subject matter is the invention of technology, that is, the study of techniques in the twentieth-century human and social sciences – as grasped through the fundamental contributions made by André Leroi-Gourhan (1911–1986). Biographical background on his life and career highlights Leroi-Gourhan’s wide-ranging scientific productions in such fields as ethnology, museology, orientalism, art history, palaeontology, behavioural psychology and prehistoric archaeology, and indeed the archaeology and anthropology of techniques. The breadth of these contributions reflects a diversity of interests, but also a form of eclecticism or ‘in-discipline’. Alongside long-standing investments in documentary and experimental practices, his writings were structured around several conceptual keywords (‘techniques’, ‘milieu’, élan vital, Homo faber, ‘liberation’, ‘exteriorization’, chaîne opératoire) which varied over time and in function of their uses. In addition, Leroi-Gourhan’s extensive archives make it possible to address the literary ambitions and intellectual practices of the scientist in action.