Virtual environments provide places for 'being there together', for avatars to interact with each other in computer-generated spaces. They range from immersive systems in which people have life-size tracked avatar bodies to large-scale spaces such as Second Life where populations of users socialize in persistent virtual worlds. This book draws together research on how people interact in virtual environments: What difference does avatar appearance make? How do avatars collaborate and play together? How do the type of system and the space affect how people engage with each other? How does interaction between avatars differ from face-to-face interaction? What can social scientists learn from experiments and other studies of how people interact in virtual environments? What are the ethical and social issues in doing this research, and in the uses of this technology? And how do virtual environments differ from other communication technologies such as videoconferencing systems and other new media? This book is a state-of-the art survey of research on these topics, and offers a framework for understanding this technology and its future implications.