How many peoples in the USSR? In what territory are they settled? What languages are spoken? What is "language building" and what role did it play in the cultural revolution of Soviet nations and nationalities? How do national cultures and languages interact? What is the role of the Russian language as the language of interethnic communication of the peoples of the USSR? All this is described in this book, covering the issues of the language life of the peoples of the USSR and the main stages of Lenin's national language policy.