The standard economic problem of optimally allocating scarce resources has, over recent decades, evolved into a set of practical and consequential policy interventions on the part of economists. Key fields of (mostly game-theoretic) microeconomics—social choice and mechanism design—have joined forces with experimental economics and, more recently, computer science to help ‘build economic machines’ (Guala 2001). In fact, a substantial share of today’s theoretical microeconomic research is directly or indirectly related to market design. It would be fair to say that the field became a key driver in the development of ‘theory’ in economics. The chapter explores the emergence of market design and its major conceptual and policy achievements. It argues that this field prompts us to challenge the traditional notion of economic models as epistemic artifacts devised by scholars to solely understand the world. Market design models also serve as instruments for intervention and accompany the actual design process in a way that could be ‘performative’. The chapter reviews existing critical work on market design, which attempts to make sense of the specific cases, contexts, and conceptual/epistemic significance of market design interventions. It also reflects on research challenges and offers some general insights drawn from the survey.