Paper is a writing material that was first invented in ancient China. Although contemporary precursors such as papyrus and amate existed in the Mediterranean world and pre-Columbian Americas, respectively, these materials are not defined as true paper. The first papermaking process was documented in China during the Eastern Han period (25-220 AD), traditionally attributed to the court official Cai Lun. During the 8th century Chinese papermaking spread to the Islamic world. By the 11th century papermaking was brought to medieval Europe, where it was refined with the earliest known paper mills utilizing waterwheels. Later Western improvements to the papermaking process came in the 19th century with the invention of wood-based papers.