Xiandi was the last emperor of the Han dynasty, since he wasn't a very strong emperor, he then got abdicated or forced to give up, the throne. Later, China got separated into three kingdoms: Wei, Wu, and Shu-Han. Without the central government, China fell into chaos.
Peasants was frustrated of their position and while the emperor's servants had too much power. So the peasants attacked the Northern China Plains during the Yellow Turban Rebellion.
Uh... I'm so frustrated that we have to do all the work and still remain poor.
After your father died, I'll turn the imperial throne to you, Cao Pi.
Every leader from the three kingdoms wanted to become the next emperor of China. Cao Cao was a general leader of the Wei dynasty, he was the strongest between the leaders. After Cao Cao died Xiandi pasted the throne to Cao Cao's son, Cao Pi.
The fall of the Han dynasty led to wars and changes in leadership. But Emperor Wendi took advantage and reunited China as one emperor for the first time in 400 years.
Leaders of the Song dynasty strengthened the education system. They also created the civil service exam, in which the candidates take the tests for government jobs. This led to the growth of restaurants, food markets, theaters, season festivals.
Song dynasty had many achievemeants. Transportation by water was very useful. Standarized currencies, mechanical clock, farming and millitary technologies, art and peoms were achievements during the Golden age in the Song.