Carl Sagan and other Cold War scientists once feared that a nuclear war could plunge the world into a deadly ice age. Three decades later, does this theory still resonate?

Is there a hidden cause of obesity? A professor at Stanford thinks the answer might lie with the 100 trillion microbes living in our bodies.

Wireless power seems cutting edge, but it was actually pioneered more than 100 years ago by Nikola Tesla. We've teamed up with the American Experience to explore how Tesla's technology is being used today.

There are over 80,000 chemicals in use today. The story of TRIS, removed from children's pajamas in the 1970s, illustrates just how hard it is to regulate chemicals, or to even know if they're safe.