They hadn't met in 175 year. Representatives from each estate came together to pass laws. It awoke ideas of sovereignty.
The third estate meets in the tennis court and make a promise to overthrow the government, then they go on to write a constitution.
The third estate needed weapons and food, so they storm the prison and got what they need and let some prisoners out while they were there.
A time when the people of the third estate took over and basically went crazy. It was a year of death, and complete chaos.
Napoleon sees that the third estate needs some stability, so he comes in and takes over. He also crowns himself as an emperor, and starts taking other nations.
In Napoleon's attempts to take over Russia, the nations come together and plan to take him over, which ended up being successful. This caused his grand empire to collapse.
The remainder of the absolute monarchs come in after Napoleon is gone, and decide how to restore peace and power throughout Europe.