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 the most prosperous period of the Han Dynasty, Emperor Wudi (140-87 B.C.) expanded from the Central Plains to the Western Regions (present-day Xinjiang and Central Asia). Emperor Wudi 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. China's 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, leading to a revolution in communications and learning.