Beta–D-poly-glucopyranose is widespread class of the natural semi-crystalline polysaccharide known as cellulose. This polymer has complicated multi-level supermolecular structure. It is built from elementary nano-fibrils and their aggregates; moreover, each nano-fibril contains ordered nanocrystallites and low-ordered amorphous nano-domains. Therefore cellulose can be a pronounced and eminent representative of nano-structured matters. Such nano matter has peculiar physico-chemical properties depending on specific surface of nano-scale constituents. In this paper, physico-chemistry of the nano-structured cellulose is discussed. In particular, the ability of nano-scale crystallites to co-crystallization and aggregation, as well as their ability to phase transformation through dissolution, alkalization and chemical modification was a subject of the investigation. Structural characteristics of paracrystalline surface layers of nano-crystallites and their effect on physico-chemical properties of the polysaccharide have been discussed.