
Extract the answer to the question from the following context.
Question: If wood is made up of cells, then what materials do those cells make up?
Context: Wood is a heterogeneous, hygroscopic, cellular and anisotropic material. It consists of cells, and the cell walls are composed of micro-fibrils of cellulose (40% – 50%) and hemicellulose (15% – 25%) impregnated with lignin (15% – 30%).

heterogeneous, hygroscopic, cellular and anisotropic material
