As a biopolymer, lignin is unusual because of its heterogeneity and lack of a defined primary structure. Its most commonly noted function is the support through strengthening of wood (xylem cells) in trees. This book presents current research in the study of lignin, including the biotechnological applications of lignin; the isolation of lignin from alkaline pulping liquors; biobleaching of paper pulp with lignin degrading enzymes; lingin and funal pathogenesis; plastic mouldable lignin and lignin valorisation into polyurethanes.