Adam Cole

What killed the dinosaurs? It's history's ultimate murder mystery, and for decades the prime suspect has been a giant asteroid. New data suggest that it struck right before the extinction. But scientists say it still may not tell the full story of what happened to the dinosaurs.

A handful of AIDS cases were first recognized in the U.S. at the beginning of the 1980s. By 1990, there was a pandemic. In 1997, more than 3 million people became newly infected with HIV. A multimedia chart lets you track the cases by country over time.

Researchers have found that a few lessons in a meditation technique adapted from Tibetan Buddhism can change the way people perceive pain.