The term user experience is becoming widely used in design and for a good reason. Maintaining a user centric perspective in multidisciplinary design work requires a commonly understood framework, such as user experience. Although intuitively understandable, user experience has lacked widely acknowledged theoretical definition. Designing for user experience addresses use in a broader experiential context, including emotions, values, expectations, actions, meanings and motivations. These issues also challenge traditional ways of understanding end users for design. This dissertation introduces an approach to understanding user experience that departs from the more traditional user or product centric approaches. This approach, co-experience, builds on an understanding of experience as social interaction. It focuses on how in and through social interaction experiences and their products come to find their place in people’s lives.