Liu Bang established the powerful Han Dynasty in 206 B.C. During the Han Dynasty, agriculture, handicrafts and commerce flourished, and the population reached 50 million. During his reign (140-87 B.C.), the most prosperous period of the Han Dynasty, Liu Che, Emperor Wudi, expanded the territory of the empire from the Central Plain to the Western Regions (present-day Xinjiang and Central Asia). He dispatched Zhang Qian twice as his envoy to the Western Regions, and in the process pioneered the route known as the "Silk Road" from Chang'an (today's Xi'an, Shaanxi Province), through Xinjiang and Central Asia, and on to the east coast of the Mediterranean Sea. Chinese silk goods were traded to the West along the Silk Road. As contacts between the East and West increased, Buddhism spread to China in the first century. In 105, an official named Cai Lun invented a technique for making fine paper, which is considered to have been a revolution in communication and learning.