Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It has been used for thousands of years for both fuel and as a construction material. It is an organic material a natural composite of cellulose fibers embedded in a matrix of lignite which resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs. In a living tree it performs a support function enabling woody plants to grow large or to stand up by them. The chemical composition of wood varies from species to species, but is approximately 50% carbon, 42% oxygen, 6% hydrogen, 1% nitrogen, and 1% other elements by weight. Wood also contains sulfur, chlorine, silicon, phosphorus, and other elements in small quantity. Certain types of musical instruments such as those of the violin family the guitar, the clarinet and recorder, the xylophone, and the marimba, are