The Han dynasty is known for the development and maturation of clerical script, or lishu, in Chinese calligraphy.
Clerical script did not appear suddenly in the Han period. Its early forms evolved from more quickly written, rectilinear varieties of the Qin-state script during the Warring States period and the Qin dynasty. Archaeological discoveries on bamboo and wooden slips show that proto-clerical forms existed before the mature style became dominant.
During the Han dynasty (202 BCE–220 CE), clerical script became the principal writing style. Its characters are generally wider and flatter than seal-script forms, with straighter structures and distinctive thick, slightly upturned stroke endings. The best-known mature form is often called Han clerical or bafen script.
Clerical script was eventually replaced for ordinary formal writing by regular script, which developed partly from clerical and related forms. It nevertheless survived as a major calligraphic style. A common oversimplification is to say that the Han invented lishu; more precisely, the Han period is when the style matured, stabilized, and became dominant.