Paper was invented in China more than 2 000 years ago. At that time, paper was made of silk and was so expensive that only the royal family and aristocrats could afford to use it. Legend has it that Cai Lun of the Eastern Han Dynasty improved the paper-making process by using tree bark and rags to create cheap and thin paper. The improvement in paper-making made paper popular, and people’s cultural life took on a new look. Later, paper was spread to the West through the Silk Road, and human civilization was also spread widely with the popularization of paper.