Abstract: In this talk, I will argue that social norms are key to solving some of the most pressing contemporary societal challenges. A proper understanding of social norms requires a complex systems perspective, in which social norms arise as an emergent phenomena in a social environment, and at the same time they drive collective behavior by affecting individuals decisions, actions and interactions. For such an approach to work, a definition of social norm that allows for their measurement in a quantitative, objective manner is required. I will discuss how economists have proposed how to do this and what can be learned by measuring social norms in several contexts. In the end, I will consider in detail the case of collective dilemmas, presenting evidence for causal effects in promoting cooperative behavior when individuals must reach a common target, e.g., to avoid the risk of catastrophic climate change or a global epidemics spread.