In 2002-2003, Russian mathematician Grigory Perelman published on the Internet a proof of the Poincaré hypothesis - the "millennium problem," for the solution of which the American Clay Institute appointed a million dollar prize. It took time for the mathematical community to recognize Perelman's achievements. However, it was not possible to present the award to the scientist: he refused it, as he had previously refused the prestigious Fields medal. A few years ago, Perelman announced that he was no longer engaged in mathematics, and minimized contacts with the outside world. The famous journalist and writer, deputy editor-in-chief of the Snob project, Masha Gessen, explores the Perelman phenomenon, relying on numerous interviews with his teachers, fellow practitioners and colleagues.