Cellulose makes up sixty percent of the wood of a tree. The rest of the wood consists mostly of lignin, which is a binding material composed, like the cellulose, of carbon, oxygen, and hydrogen, but of an entirely different and more complicated chemical structure than cellulose. Fifty years ago, lignin was considered a not so useful product as cellulose, research has helped to develop valuable products from it.

Besides cellulose and lignin, wood contains a small quantity of different substances—starch, fats, sugar, resins, tannins, and many others—and is literally saturated with water.