The article presents Katarzyna Kobro's innovative contribution to the sculpture of the 1920s and 1930s. Born in Moscow, Kobro may have been educated by Kasimir Malevich and Vladimir Tatlin , whose works influenced her artistic formation. The most original and important of her works are the Unistic sculptures. The main postulate of the Unistic theory regarding sculpture was unity of the work of art and its environment. An Unistic sculpture had to maintain links with space; to achieve this, the solid, which closes off the sculpture from space, had to be renounced. The very first sculptures to renounce the solid were Kobro's "spatial compositions", constructed so as to form a continuum with infinity and with time. Their extremely simple structure, capable of both penetrating and absorbing space into itself, was in accordance with the Unistic theory which stated that a sculpture does not exist for its own sake, its aim being to sculpt space. In 1945 Kobro donated all her sculptures to the Muzeum Sztuki in Łódź, where they can be seen today, displayed in the "Neo-Plastic Room" designed by Kobro's husband, Władysław Strzemiński.