When did Chinese characters really develop into an art in China?

The process of Chinese characters becoming calligraphy art is as follows:

Qin and Han dynasties-spontaneous stage

Wei, Jin, Southern and Northern Dynasties-conscious stage (Chinese characters developed into conscious calligraphy art, and there was a "calligrapher" Wang Xizhi in the Eastern Jin Dynasty)

Sui and Tang Dynasties-Calligraphy reached a new peak (calligraphy theory became more and more mature, cursive and regular script).

Song Dynasty-Calligraphy art has its own system, pursuing individuality and ignoring statutes.

Ming dynasty-calligraphy was further popularized and secularized.