Before the Qin conquest of the other regions of China, regional characters were used, and under unification of China, currency, laws, weights and measures and writing was to be systemised. Thus, the characters which were different to those found in Qin were discarded, and Li Si's xiaozhuan character became the standard.
Li Si's compilation is known only through Chinese commentaries through the centuries. It is purported to contain 3,000 characters. The name of the work gives rise to the style of characters used, "small seal script".
Xiaozhuan (小篆), or Hsiao-chuan was the title of a work on Chinese characters compiled by Li Si during the reign of the First Emperor of China, Qin Shi Huang.
Thus, the characters which were different to those found in Qin were discarded, and Li Si'sxiaozhuan character became the standard.
Li Si's compilation is known only through Chinese commentaries through the centuries.
What Li did, in effect, was to simplify the ancient zhuan (small seal) script.
2) The lishu (official script) came in the wake of the xiaozhuan in the same short-lived Qin Dynasty (221 - 207 B. This was because the xiaozhuan, though a simplified form of script, was still too complicated for the scribes in the various government offices who had to copy an increasing amount of documents.
Cheng Miao, a prison warden, made a further simplification of the xiaozhuan, changing the curly strokes into straight and angular ones and thus making writing much easier.