Challenging mainstream practices and bringing about contextually appropriate, more sustainable ways of living requires changes much more significant than simply doing the things we currently do, but more efficiently. Across research projects the authors Adrian Clear, Kirstie O'Neil and Adrian Friday, Lancaster University, became intrigued by significant changes in practice that occurred during life transition. By life transitions, the authors are referring to situations such as changing residences, having children, or retirement, where ways of doing things are developed anew, or broken down and rebuilt over time. The research showed that a promising route for design, then, is to support transitions as longer-term and more fundamental processes of change. This involves designing interactions that support the development of necessary elements of practice, related to materials, competencies, and meanings that help guide or even instigate transitions in practice in a sustainable direction. Doing so opens up interesting questions for HCI in terms of realizing systems and interfaces that evolve with users as they engage in a course of practice and life transitions, and how an ecology of interactions might work together to support change in a number of interrelated areas of everyday life.