The regular script which absorbed some elements of official script epitomized the Sui Dynasty's calligraphy. The Tang Dynasty's calligraphy can be divided into three periods: the early Tang, the middle Tang and the late Tang. The Big Four of the Early Tang, Ou Yangxun, Yu Shinan, Chu Suiliang and Xue Ji, esteemed Jin's powerful style and became its earnest followers. The Middle Tang is represented by its achievements in regular script and cursive script. Li Yong created a unique style when he wrote inscriptions for stone steles in running hand. Yan Zhenqing inherited traditional ideas and pushed the regular script to perfection. Zhang Xu and Huai Su's wild cursive script broke through the acquired rules and formed a completely new genre. Liu Gongquan was the most outstanding calligraphist of the late Tang. His style is slim and strong while Yan Zhenqing's is foursquare, dignified and serene. Together they are called "Yan's muscles and Liu's bones".