The published data on the chemical and physical modifications of cellulose aimed at creation of a wide variety of new innovative materials for hi-tech and priority directions in the development of science and engineering are summarized. Investigations into the chemical modification of cellulose via nucleophilic substitution, regioselective insertion of functional groups, graft copolymerization, oxidation, and esterification are covered. The importance of studies dealing with the search for new solvents of cellulose aimed at extension of the potential inherent in its modification and processing and in the design of nanocellulose-based materials is emphasized. On the basis of analysis of the literature data, the potential for creation of new functional materials for biomedical investigations, medicine, and electronics is shown.