Book excerpt: This book is part of a two-volume work that constitutes the refereed proceedings of the 11th IFIP TC13 International Conference on Human-Computer Interaction, INTERACT 2007, held in Rio de Janeiro, Brazil in September 2007. It covers tangible user interfaces and interaction; cultural issues in HCI; safety, security, privacy and usability; visualizing social information; online communities and e-learning; children, games, and the elderly; as well as software engineering and HCI.