bA comprehensive overview of developments in augmented reality, virtual reality, and mixed reality--and how they could affect every part of our lives.bpAfter years of hype, extended reality--augmented reality AR, virtual reality VR, and mixed reality MR--has entered the mainstream. Commercially available, relatively inexpensive VR headsets transport wearers to other realities--fantasy worlds, faraway countries, sporting events--in ways that even the most ultra-high-definition screen cannot. AR glasses receive data in visual and auditory forms that are more useful than any laptop or smartphone can deliver. Immersive MR environments blend physical and virtual reality to create a new reality. In this volume in the MIT Press Essential Knowledge series, technology writer Samuel Greengard offers an accessible overview of developments in extended reality, explaining the technology, considering the social and psychological ramifications, and discussing possible future directions. pGreengard de