Ultracold neutrons — discovery and research

A review of the progress in the physics of ultracold neutrons (UCN), starting with the first experimental studies, is given. Problems dealt with by the author under the supervision of Fyodor L'vovich Shapiro are presented. It is shown how these problems were gradually solved and how their relation to other issues in physics was revealed. A review of the present status of UCN physics is given, and the prospects are discussed.