Will video games change the way we learn? We argue here for a particular view of games--and of learning--as activities that are most powerful when they are personally meaningful, experiential, social, and epistemological all at the same time. From this perspective, we describe an approach to the design of learning environments that builds on the educational properties of games, but deeply grounds them within a theory of learning appropriate to an age marked by the power of new technologies. We argue that to understand the future of learning, we have to look beyond schools to the emerging arena of video games. We suggest that video games matter because they present players with simulated worlds: worlds that, if well constructed, are not just about facts or isolated skills, but embody particular social practices. Video games thus make it possible for players to participate in valued communities of practice and as a result develop the ways of thinking that organize those practices. Most educational games to date have been produced in the absence of any coherent theory of learning or underlying body of research. We argue here for such a theory--and for research that addresses the important questions about this relatively new medium that such a theory implies.