This book presents the chemical properties of lignocellulosic fibers, knowledge of which is essential for innovation and sustainable development of their transformation. Thermochemical transformation of wood and other lignocellulosics is presented to highlight its volatile, liquid and solid products and their novel applications. Forest biorefinery is described to emphasize the new products from lignocellulosic constituents, both structural (cellulose, hemicelluloses and lignins) and those extraneous to cell walls-extractives. New developments in cellulose technology related to nanocellulose are discussed in relation to new applications. Industrial lignins are presented in detail, both in terms of extraction procedures from spent liquors and structural characterization of the isolated lignins. Application of lignocellulosic biopolymers in new composite materials, or in biomaterials for medicinal purposes, and in solid wood preservation, are described. The example of an industrial biorefinery installed in southwestern France more than 40 years ago is presented.