Cotton is the single most economically important natural textile fiber in the world. It is a seed hair and has historically composed a large portion of the world's textiles. The plant is grown in most tropical and subtropical regions of the world. The demand for cotton, especially as a garment fiber, it due to properties such as its soft hand, water absorption, spinnability, and dyeability, and to its ease of home laundering. Perhaps cotton's most important textile property is its comfort. These properties are due to the unique, multilayered construction of the fiber subunits. The nature of this construction has been studied microscopically for more than 100 years, first using light microscopes, then electron microscopes as they became available. Because they are natural biological materials, no two cotton fibers are exactly alike. Yet they do have certain structural features in common. Structure in cotton can refer to several levels of construction.