This chapter draws on the theory of Thomas Malone and describes several features of intrinsically motivating environments, such as responsiveness, curiosity, challenge and fantasy. These features include competing theories about what makes computer games fun and how interactions with computer games can lead to further learning. An activity is intrinsically motivating if the learners are engaged in it for their own sake. However, no single instructional game can be expected to appeal to everybody. An accountable environment permits the learners to explore freely and make full use of their capacities for discovering relations of various kinds. Making learning more fun will produce corresponding increases both in learning and retention, and in subsequent interest in the subject matter itself. This chapter will also provide examples of intrinsically motivating instructions in science, based on different environmental features.