Matthew Connelly, Professor of History and Co-Director of the Institute for Social Science and Economic Research and Policy (ISERP) at Columbia University, just recently published a new book, The Declassification Engine. His work traces the nature of secrecy in the United States, demonstrated by the over-classification of documents. In this first episode of our new podcast series, Espresso with the Experts, Leila and Bea discuss the research which went into his new book, along with his work with the History Lab, a lab at Columbia which uses data science tools, natural language processing, and machine learning tools in order to analyze historical data.