Color, lustre, odor, taste, texture, grain, figure, weight, and hardness of wood are all sensory properties. These additional macroscopic properties might be used to describe a piece of wood for identification or other purposes. Microscopically, wood is made up of parallel, elongated fibers called tracheids that contain large amounts of lignin and few other organic compounds. Wood is an important material for humans because of its use for building materials and fuel. In addition, it has many other applications including as an industrial material, in agriculture as a soil amendment, and as a bioresource. Wood is produced by secondary growth from the trunk of a tree or shrub. It consists primarily of polysaccharides (carbohydrates) that are converted into cellulose through a series of reactions with water and oxygen present in the atmosphere. The transformation starts with the formation of coniferous trees which produce new shoots that grow out horizontally from the trunk. New leaves develop at the tip of each shoot. As the branches spread out, they form roots which eventually reach down into moist soil where they can find moisture and nutrients needed for healthy growth. All green plants require light energy from the sun to function properly. However, not all plants have chlorophyll, the chemical that allows them to capture sunlight and use it for their own needs. Without this ability, they could not make food nor create oxygen.