Seal script or sigillary script is a style of writing Chinese characters that was common throughout the latter half of the 1st millennium BC. It evolved organically out of bronze script during the Zhou dynasty (1046–256 BC). The variant of seal script used in the state of Qin eventually became comparatively standardized, and was adopted as the formal script across all of China during the Qin dynasty (221–206 BC). It was still widely used for decorative engraving and seals during the Han dynasty.