This chapter explores the development of Russian modernism and avant-garde trends into the 1920s in relation to the new institutions of the Silver Age (1890s–1917), pausing on why the period has proven hard to define. It discusses key modernist journals and the social contexts, including groups and societies, that were formative for writers. How these cultural processes changed in Soviet Russia under a regime of political and aesthetic state control, and in Russia Abroad, is charted. While Socialist Realism became the dominant aesthetic from the 1930s, the chapter shows how innovations in language and theory (including Formalism and structuralism) as well as independent literary institutions bypassed official doctrines and led to important experimentation. The chapter tracks a number of phenomena bridged unofficial literary culture and the post-Soviet literary field.