Sustainability is a broad topic usually linked to biological and ecological systems. Sustainability science was born as a new discipline at the World Congress on Challenges of a Changing Earth in 2001 (Kates et al. Science 292(5517):641–642, 2001). In this book, I focus on sustainability of artifacts (systems that are built by people) and more specifically tangible interactive systems (TISs). What does it mean to design a sustainable TIS? Basically, a TIS should allow easy modification and maintenance. Ideally, it should be self-sustainable. Therefore, taking sustainability seriously in design is thinking about possible futures of the artifacts that we are designing. Sustainability means thinking about people who, in the future, will deal with systems that we are designing today. Sustainability means thinking about life cycle of a system from creation and design to decommissioning.