The document provides an overview of the unification of China under the Qin and Han dynasties. It describes how the Qin dynasty first unified China under Emperor Qin Shi Huang in 221 BCE, establishing a centralized bureaucracy and standardizing the currency, script, and legal system. However, resistance to Qin policies led to its collapse in 207 BCE. The Han dynasty then ruled China from 206 BCE to 220 CE, maintaining political unity while relaxing some Qin policies. The Han adopted Confucianism, expanded the empire, and saw advances in technology, population growth, and prosperity, though difficulties grew over time.