The idea for this book has been with me for quite some time. It first emerged when, in the fall of 2007, the global financial system began to teeter toward the abyss. The speed of the unfolding crisis left little time for deep thinking, but once the eye of the storm had passed, I, along with many others, sought to discover what might explain finance’s stupendous expansion in recent decades, and what accounted for its steep fall. Together with collaborators from different disciplines, I aimed to unpack the institutional structure of different segments of financial markets, one at a time. To me, the most revelatory part of our findings was how familiar the basic building blocks of the financial system looked, notwithstanding the fanciful assets that had been created more recently and the system’s unparalleled complexity. Everywhere we probed a little deeper, we found the core institutions of private law: contract, property, collateral, trust, corporate, and bankruptcy law. They had powered the expansion of markets in financial assets, but, as it turned out, they were also key determinants in their undoing. When actual returns on these assets started falling behind expected returns, asset holders enforced their legal entitlements: they made good on the collateral calls, credit lines, repo contracts, and bankruptcy safe harbors, and in doing so, they helped deepen the crisis. Some still got out in time, but many others found themselves with assets that no one would take, except the central banks of select countries.