Jimmy Wales and Larry Sanger launch Wikipedia, a free online encyclopedia written collaboratively by volunteers.
Al-Qaeda hijackers attack New York and Washington with four airliners, killing nearly 3,000 people.
A US-led coalition invades Iraq and topples Saddam Hussein, beginning a long period of occupation and conflict.
The Human Genome Project announces it has sequenced the vast majority of the human genome.
Larry Page and Sergey Brin incorporate Google, which becomes the world's most widely used search engine.
The Zarya module is launched from Baikonur, beginning assembly of the multinational International Space Station.
Mark Zuckerberg and fellow students launch the social network Facebook at Harvard; it later reaches billions of users.