While ancient Egyptians used papyrus, the first true paper-making process—creating a felted sheet from plant fibers—is credited to Cai Lun, a court official during the Han Dynasty. He used a mixture of mulberry bark, hemp, old rags, and fishnets, which were pulped, diluted, and then strained through a screen. This invention provided a lightweight, affordable, and durable medium for writing, which was a massive improvement over heavy bamboo slips or expensive silk. The availability of paper fueled the spread of literacy, the recording of history, and the administration of the vast Chinese empire. The technology remained a closely guarded secret in China for centuries before spreading to the Islamic world following the Battle of Talas in 751 AD, and eventually to Europe. Paper is considered one of the 'Four Great Inventions' of ancient China that shaped the modern world.