Hurricane Katrina strikes the US Gulf Coast, breaching New Orleans' levees and killing more than 1,300 people.
Mark Zuckerberg and fellow students launch the social network Facebook at Harvard; it later reaches billions of users.
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.
Steve Jobs unveils the first iPhone, accelerating the era of touchscreen smartphones.
Barack Obama wins the presidential election, becoming the first African American elected to the office.
Jimmy Wales and Larry Sanger launch Wikipedia, a free online encyclopedia written collaboratively by volunteers.