Risk reasoning has become the common-sense mode of knowledge production in the health sciences. Risk assessment techniques of modern epidemiology also co-shape the ways genomic data are translated into population health. Risk computations (e.g., in preventive medicine, clinical decision-support software, or web-based self-tests), loop results from epidemiological studies back into everyday life. Drawing from observations at various European research sites, I analyze how epidemiological techniques mediate and enact the linkages between genomics and public health. This article examines the epidemiological apparatus as a generative machine that is socially performative. The study design and its reshuffling of data and categories in risk modeling recombine old and new categories from census to genomics and realign genes/environment and nature/culture in novel and hybrid ways. In the Euro-American assemblage of risk reasoning and related profiling techniques, the individual and the population are no longer separate but intimately entangled.