At first, their work was made of black gauze. When the Eastern Jin Dynasty proclaimed itself emperor, everyone who worked in Jiankang Palace in the capital had to wear royal robes. Later, their work was also widely circulated among the people and became a kind of hat that people often wear.
Since the Sui and Tang Dynasties, their work has become an official "official costume". At that time, all the officials of Tiandi wore their black hats. In order to distinguish grades, the Sui Dynasty decorated black hats with jade ornaments, and expressed the size of official positions by the number of pieces: usually nine pieces of one product, eight pieces of two products, seven pieces of three products, six pieces of four products, five pieces of five products, and jade ornaments are not allowed under six products. In Song Taizu's Zhao Kuangyin era, the black hat had a new change, that is, a wing was added to each side of the hat. This is to prevent courtiers from whispering to each other during the deliberation, so that as long as the head moves, the soft wings will flicker and tremble, and the emperor will be condescending and see clearly.
Their work became the "patent" of civil and military officials, which began in the Hongwu period of the Ming Dynasty. Zhu Yuanzhang stipulated that all civil and military officials should wear official uniforms when they go to court, and civilians should not wear them.
In the Qing Dynasty, officials no longer wore official posts, but people still used to regard "official posts" as the symbol of officials. "Unemployment" means being fired for the people.