Cai Lun, born in Guiyang (today's Chenzhou, Hunan Province) during the Eastern Han Dynasty, was a paperwork secretary (Zhong Chang Shi) of Emperor He and an improver of papermaking.

Cai Lun became an eunuch in palace during the reign of Emperor Ming, and was promoted from the post of Xiao Huang Men during the reign of Emperor Zhang to paperwork secretary during the reign of Emperor He, and then the Shang-fang ling in charge of imperial utensils in the ninth year of Yongyuan (97 A.D.). For papermaking, he made some improvements by trying materials like bark, hemp, rags and even old fishing net in a series of processes such as breaking, smashing, frying and drying. Paper was thus made with its quality further enhanced by means of boiling the raw materials with lime. In the seventeenth year of Yongyuan (105 A.D.), Cai Lun presented his paper to Emperor He, which was well known as "Marquis Cai" paper for its low cost, wide choices of materials and convenient popularization.

The invention of papermaking technique made great contributions to the progress of Chinese and world civilization. However, during the Eastern Han Dynasty and Three Kingdoms period, paper was not widely popularized, and people still tended to use primarily the earlier writing materials of bamboo and silk. Up until the Jin Dynasty, the craft of papermaking was spread to the Yangtze River basin, where featured rich papermaking materials and emerged paper of better quality, thus making paper more widespread. Moreover, thanks to the prevalence of paper, book copying and collecting became popular among the people of Jin Dynasty. Later, Cai Lun was esteemed as the founder of papermaking.