Prof. Dr. Heinz Mandl is Professor Emeritus of Educational Science and Educational Psychology at Ludwigs Maximilian University Munich (LMU). His academic career focused on learning and instruction, especially on knowledge acquisition from text and pictures, design of digital learning environments and net-based knowledge communication in groups, overall the gap between knowledge and action. After working as teacher, he studied psychology at LMU where he earned his doctorate. Afterwards he worked as assistant professor at University Augsburg and become full professor at University of Tübingen before he returned to LMU in 1990. He received the Oeuvre Award for Outstanding Contributions to the Science of Learning and Instruction from EARLI. In applied areas his research significantly influenced technology-enhanced learning and knowledge management.Nancy L. Stein was at the time of original publication based at the University of Chicago, USA.Tom Trabasso was at the time of original publication based at the University of Chicago, USA.