The king and queen are spending far too much money, from wars to palaces. The nation is going bankrupt, but it can't get more money due to the unfair taxation of the third estate, which sparks revolutionary ideas combined with the Enlightenment.
At the Estates General, the Third Estate opted for reformation of society. Instead, the other two estates said no. The Third Estate changed its name to the National Assembly, and published a Declaration of Rights and Humanity.
On July 14, 1789 the French Revolution began in when peasants stormed the Bastille, a political prison. Peasants also stormed manors in an attempt to gain titles and land.
After constant invasion from other countries to restore the monarchy, a new ruling body was established called the National Convention under a new constitution, that cut ties with the Catholic Church. The National Convention moved quickly to execute the royal family.
In response to foreign threats, the Committee of Public Safety was created, led by Robespierre, and the constitution was suspended. In the name of eliminating enemies of the republic, the Committee executed between 30,000 and 50,000 people. Eventually Robespierre was overthrown, ending the Reign of Terror.
In the chaos created by the revolution, Napoleon Bonaparte swooped in and quickly established absolute power in France. He modernized France under the Napoleonic Code, public education, and creation of a national bank.