The Natural Step framework for sustainability is unique, science-based approach developed in 1989 and refined ever since. It is a way of seeing the world that helps decision-makers put sustainable development into action. In this Schumacher Briefing, David Cook tells the story of the evolution of the organisation from its start in Sweden to the present day. Whilst the fundamentals of TNS remain the same, it has responded to the ever-evolving sustainability debate. David provides an overview of the TNS framework here.