What is international science and how does it function? This book answers these questions through a detailed study of international congresses on genetics held from 1899 to 1939. It presents a portrait of international science as a product of continuous interactions that involved scientists and their patrons within specific political, ideological, and disciplinary contexts. Drawing on a variety of archival sources - ranging from Stalin's personal papers to the records of the Gestapo and from the correspondence among scientists in different countries to the minutes of the Soviet government's top-secret meetings - it depicts the operations of international science at a time of great political tensions. Arguing that personal networks constitute a major structural component in the discipline's formation, Krementsov traces the emergence of international networks in genetics and explains their role in shaping the international community's reaction to national developments which threatened to undermine the very standing of genetics as an international discipline and which, in the end, profoundly affected the fate of the congress and the fate of the discipline.