The book is devoted to the influence of Russian scientists (statisticians, ethnographers and specialists in demography) on the practices of managing the empire and the heterogeneous dynamics of the life of its constituent peoples in the turning point of half a century of history - from the era of counter-reforms of Alexander III to the pre-war Stalinist terror. The author explores the contribution of social scientists to the formulation of criteria for ethnic identity (from linguistic to economic and geographical) in the era of national awakening and fundamental breakdown of the former social system. The interaction of science and politics has been studied in detail using the example of organizing general censuses of 1897, 1926, 1937 and 1939 and processing the thoughts of their materials. J. Cadio shows that changes in domestic "nation studies" after 1917 expressed not only the aspirations of the new government, but also the rapid development of federalism and national cultures on the ground, as well as the legacy of previous academic and administrative traditions.