The development of hybrid materials, associating a polymer with metallic fillers, is currently attracting exceptional interest. The direct grafting of nanoparticles on the surface of fibers also opens up new technological developments. The appearance of nanocellulose has allowed the development of innovative materials, created from microfibrils or cellulose nanocrystals. Both can be functionalized before being incorporated into other materials, particularly into polymers to form composites with specific properties. The control of chemical processes involving chemical modification of the cellulose skeleton, in bulk or on the surface, is essential to control and optimize the properties of new materials and their use. The alcohol groups are involved in inter and intramolecular hydrogen bonds with neighboring chains, which modifies the chemical reactivity with respect to each other. However, these hydroxyl groups can react with different organic molecules (isocyanates, amines and others) producing cellulose derivatives with specific properties.