During the 20^th century, Russia and the Soviet Union were world leaders in mathematics. This collection of essays celebrates outstanding events and people in the development of twentieth century mathematics, representing a wide variety of specialties in which Russian and Soviet mathematicians played a considerable role. The articles are written in an informal style, covering a range of topics from mathematical philosophy to the description of the development of ideas. Many give a unique account of personal meetings with famous representatives of twentieth century mathematics who exerted great influence in its development.