Designers are choice architects: they create the environments within which our decisions are made. The growing fields of behavioural economics and decision science provide empirical foundations on which to build better choice architecture. The findings show that our decisions are systematically influenced by how they are framed. We change our decisions according to default options, levels of risk and uncertainty, relative comparisons, the potential for losses, cognitive costs, timing of rewards and social norms. By understanding these core principles of human decision-making, designers can create choice architecture that improves our decisions and, consequently, our wellbeing.