This book is about the mechanism of technology trees, used to represent the history of technology in historical strategy games. In these games, the progress of technology is captured in complex tree-like diagrams. How do they represent technological progress, what technologies are selected and how does this relate to both real history? Balancing on the disciplinary crossroads of game studies and science and technology studies, this book explores this curious 'tech tree' mechanism by comparing four strategy games: Civilization 4, Age of Empires, Rise of Nations and Empire Earth. After introducing the basics of strategy games, the book explores the various technology tree mechanisms in depth (including helpful illustrations). It deals with the tricky in game representation of time and history. Three types of technological determinism are exposed in tech trees. Finally it includes a comparison of the selection, function and depiction of technologies. This book is relevant to both science and technology scholars interested in the representation of the history of technology in popular culture, and videogame scholars looking for an in-depth exploration of this mechanism.