Funding development requires access to financial resources. While this causal-ity is commonsense, the underlying complexity and struggle has accompanied international development organizations ever since they were founded. The objective of the 2020 aiib Legal Conference and the 4th Volume of the aiibYearbook of International Law is to take stock. Taking stock requires us to look back on the history of international development organizations and analyze how their funding models have evolved over time. But taking stock shall also provide answers to how some of the most pressing issues of our time can be addressed and financed, while acknowledging the key role that international development organizations have in this challenge.