The book deals with the challenges that arise when virtual worlds are used for learning and teaching. The ideas and practices emerging from this field are relevant to all educators, and offers insights into the development of a pedagogy that is authentic, inclusive and enjoyable. Each chapter addresses a particular issue and is illustrated with examples drawn from both research and practice. These examples cover a wide range of learning scenarios, both formal and informal, involving teenagers, school pupils, undergraduate and postgraduate students as well as a variety of lifelong learners. The issues include the importance of virtual worlds, the influence of online games and physical-world economics and politics, the relationship between avatars and learner identity, the challenges of ensuring child safety and protection, interaction between real-world and in-world environments and activities, accessibility and the development of new pedagogues. The authors are all teachers and learners in virtual worlds; many have been responsible for designing, programming and maintaining virtual environments.