Although the Internet takes us everywhere in cyberspace, it usually requires us to be seated behind a desk. In contrast, the cellphone lets us walk through the world, fully connected. Cellphone explores the history of mobility in media--from books to cameras to transistor radios to laptops--and examines the unique impact of a device that sits in a pocket or palm, and lets us converse by voice or text. The restricting and liberating edge of accessibility transforms restaurants, public transport, automobiles, romance, literacy, parent-child relationships, war, and indeed all walks of life, trivial and profound. Like an organic cell that moves, evolves, combines with other cells, and generates, the cellphone has become a complex sparkplug of human life.