Rydberg matter is a condensed excited state made of highly excited atoms. State of art of research in the field of Rydberg matter is briefly reviewed. Special attention is focused on the contribution of Russian and Swedish scientists' groups to the analysis of this problem. Most attention is concentrated on physical principles of pseudopotential method and density functional theory used to describe the Rydberg matter. The description of Rydberg matter as an excited state becomes viable after the formal replacement of excited atoms by ground state pseudoatoms. This procedure has been used to find
parameters of Rydberg matter made of highly excited cesium atoms. Theoretical estimations conform to experimental data available.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.