Lignin
Lignin is one of the three main substances that make up wood. The other two are carbohydrates and extractives. Lignin is an amorphous, highly polymerized substance that makes up the lamella. The lamella is the intercellular material that holds the fibers together. The structure of lignin consists of phenyl propane units linked together in 3-D. Some of these links are broken in the pulping process to separate the fibers.