Liu Bang established the powerful Han Dynasty in 206 BC. During the Han Dynasty, agriculture, handicrafts and commerce flourished, and the population reached 50 million. During his reign (140-87 BC), the most prosperous period of the Han Dynasty, Liu Che, Emperor Wudi, expanded the territory of the empire from the Central Plains to the Western Regions (present-day Xinjiang and Central Asia). He twice dispatched Zhang Qian 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 eastern shores of the Mediterranean. China's gorgeous silk goods were traded to the West along the Silk Road. As contacts between East and West increased, Buddhism spread to China in the first century AD. In 105, an official named Cai Lun, synthesizing the experience of those before him, discovered a technique for making fine paper, an invention that led to a revolution in communications and learning.