The book of Doctor of Historical Sciences Valentina Alexandrovna Tvardovskaya is devoted to the biography of the revolutionary Nikolai Alexandrovich Morozov (1854-1946), who during almost 30 years of imprisonment in tsarist prisons became a prominent scientist who enriched Russian and world science with his works. From the book, the reader learns about Morozov's participation in "going to the people," in the largest revolutionary populist organizations "Earth and Freedom" and "Narodnaya Volya," about his activities in exile. The author talks about Morozov's meetings in London with Karl Marx. The book is designed for a wide range of readers interested in the history of the revolutionary movement in Russia.