New institutional economics (NIE) studies the rules and norms that humans devise to reduce uncertainty and control their environment, both formal institutions, such as written contracts and laws, and informal institutions, such as societal norms. NIE is an exceptionally dynamic field and, as this introductory chapter attests, this second edition of the Handbook covers a wealth of new research and novel methodologies. It includes a new section on culture and informal institutions and new chapters on local politics, authoritarian institutions, platforms, relational contracts, and more. Many chapters from the first edition incorporate new discoveries in this rapidly changing field. This edition, like the first, covers both branches of NIE. As North defines it, “Institutions are the rule of the game in a society,” while organizations are the players, a distinction which delineates the two branches. The “Northean” branch focuses on the fundamental ground rules of the institutional environment and the “Williamsonian” branch on organizations and their governing institutions.