The growth model of the 20th century required that designers and companies achieve economies of scale. Scaling up involved abstraction to make large-scale production possible for the global industrial economy. In the 21st century, social challenges are increasingly disrupting world markets. This changes the focus of the design process. Designers once needed to learn just a little about large groups of people to serve mass markets. Today, they must learn a great deal about relatively small numbers of people. They must shift from concentrating on what makes groups of people similar to what makes them different. This article explores the process of “scaling down” by describing key principles. It examines these principles at work in three case studies from The Helen Hamlyn Centre for Design to develop a lighting system for inner-city housing estates, a planning tool to create better workplaces, and a suicide-prevention strategy for a public health black spot.