This volume presents a scientific and practical trend in lifelong education, which focuses on "human activity". This trend is particularly apparent in French speaking countries where a seminal tradition of ergonomics, born in the middle of the 20th century, produced studies about work and workers’ activity in various contexts. Results demonstrate that working activity, firstly, is always complex, creative and enigmatic despite the efforts done by the designers to create prescribing working environments and by managers to control production procedures, and secondly, cannot be understood without specific field studies about real work. This approach influenced adult educational researchers and trainers to develop programs in order to help trainers to better know human activity and its transformations in various social practices (and not only in working context). It also helps them to design learning environments accompanying human activity transformations at various time scales. The chapters in this volume present a range of original studies on human activity in various social practices, such as tourism, theatre prop-makers in opera, manual job environments, management in a small company, high level athletes illegal practices, school teaching and finally during teachers retirement ceremonies. These studies of the relationships between social practices and human activity and its transformations, give empirical and conceptual bases for designing programs aimed at emphasizing and accompanying specific individual and collective learning, and human development in a lifelong perspective. This book was published as a special issue of International Journal of Lifelong Education.