In Chapter 3, we provide an overview of sensitive information in global governance and important historical context. The chapter first describes new data on the confidentiality features of a sample of 106 IOs. We review variation in the frequency and form of such protections and show that measures to protect various forms of sensitive information are surprisingly common and vary in interesting ways. The chapter then describes the rise of the norm of transparency in diplomacy and global governance after World War I, which then deepened with the end of the Cold War. This is juxtaposed with early examples of IOs experimenting with confidentiality and sensitive information. The chapter concludes by explaining how changes in technology and broader cooperative goals have generally led to efforts to integrate sensitive information into IOs, despite the resulting tension with transparency.