This review covers some trends and approaches to the study of inorganic polyphosphates that originated from the fruitful ideas and pioneering works of A. N. Belozersky. This is, first of all, the elucidation of a close relationship between these biopolymers and nucleic acids in organisms at different evolutionary stages; second, the study of "fossil" reactions in polyphosphate metabolism that permit an understanding of their role in the evolution of phosphorus turnover and cell bioenergetics; third, the possible use of the conservative enzymes of polyphosphate metabolism, e.g., exopolyphosphatases, as molecular chronometers for obtaining additional data concerning the theory of the endosymbiotic origin of eukaryotic cells from prokaryotes.