Recent progress in metagenomics resulted in rapid accumulation of data on genetic diversity of microorganisms. This diversity is mostly represented by uncultured microorganisms, never described in regard to phenotype. Therefore, former phenotypic classification system of bacteria came out to be inapplicable to metagenomics and was thus replaced with a genotypic system, built upon the 16S rRNA gene. Metagenomics operates with nucleotide sequences instead of species. This shift in biodiversity assessment required a new classification system. In this study, we attempted to develop such a system. We call it the Evolutionary Space (ES). ES is a metric multidimensional space, where each point represents a single 16S rRNA sequence. These points are geometrically spaced according to the genetic distances between corresponding sequences. ES is aimed to represent genetic variability of all currently existing and theoretically predicted 16S rRNA genes and to identify obscure evolutionary patterns defining this enormous