Imagine trying to write down everything humans know about everything. That is exactly what Denis Diderot tried to do. Born on October 5, 1713, in France, Diderot spent over 20 years creating the *Encyclopedie*, the first modern encyclopedia. The project was massive. It had 72,000 articles written by over 150 experts. There were detailed drawings of machines, buildings, and scientific tools. Diderot did not just want to collect facts. He wanted to teach people to think for themselves. At the time, the Catholic Church and the French king controlled what people could learn. Diderot's encyclopedia included articles on science, philosophy, and government that challenged their authority. The powerful were not happy. Diderot was thrown in prison. The encyclopedia was banned. But copies kept spreading. People read it in secret. The ideas inside helped start a movement called the Enlightenment. People began demanding the right to think freely, govern themselves, and question authority. Some historians believe the encyclopedia helped cause the French Revolution. All because one man wanted to put knowledge in the hands of ordinary people.