Cultural-historical activity theory is a powerful toolkit for social sciences. This book demonstrates how the Finnish school of developmental work research uses activity theory in the analysis and practical transformation of work, technology and organizations. Developmental work research is a longitudinal and interventionist approach. Researchers aim at generating, supporting and following cycles of expansive learning in the activity systems they study. The process opens up qualitatively new possibilities for creating use values and for developing the capabilities and agency of the practitioners and their clients. Critical dialogue and partnerships are built between the researchers and the organizations they study. In their 18 chapters, the 23 authors of the book give a broad sample of work done over a period of ten years in the Center for Activity Theory and Developmental Work Research at University of Helsinki. The theoretical and methodological themes range from the polyphony of activity to relationships between history, ethnography and interventions. The empirical chapters range from the work of teachers and judges to collaboration between industrial enterprises. Yrjö Engeström is Professor of Adult Education and Director of the Center for Activity Theory and Developmental Work Research at University of Helsinki. Joachim Lompscher (1932-2005) was Professor Emeritus of Educational Psychology at University of Potsdam. Georg Rückriem is Professor Emeritus of Education at the Hochschule der Künste in Berlin. Cover photo: Faces of the authors in the order of their chapters.