The extraction of cellulose nanofibers and crystals has gained a large interest not only inthe academic research society but also in industries during the last few years. We cansee many ongoing activities today and it is obvious that the world largest forestcompanies believe that nanocelluloses will lead to new use of forest resources. The usesare expected to be new light weight composite materials to be used in transport,electronic applications but nanocelluloses can also be used in cosmetics and medicalapplications. This presentation deals on processing methods of nanocelluloses,including mechanical and chemical isolation of nanofibers and nanocrystals. Themechanical methods are ultra fine grinding and high pressure homogenization and thechemical method is acid hydrolysis. The extracted nanofibers are usually around 20-30nm in diameter and the length is estimated to be in μm range while the nanocrystals aremuch smaller, being about 3-5 nm in diameter and 200 nm in length. The properties ofthe cellulosic nanomaterials from natural resources (wood, bioresidues, annual plants)have shown to be very similar independent of the original source, meaning that the sizedistribution of nanofibers is an important factor. The main difficulty when producingcellulose-based nanocomposites is to disperse the reinforcement in the polymer matrixwithout degradation of the polymer or the reinforcing phase. Therefore most commonway to prepare cellulose nanocomposites is to impregnate the “cellulose nanopaper” bya polymer resin or use of solvents to disperse the nanofibers or crystals in a solvedpolymer. Our group has also studied possibilities to disperse nanocelluloses in polymermelt using common melt processing technologies, which is a suitable method toproduce nanocomposites in larger scale.