This Storm Chaser Risked It All for Tornado Research

Tornado chasers in a van track an "elephant's trunk" tornado in South Dakota. Storm chaser Tim Samaras made his career gathering data from inside tornadoes, using an instrument that he invented and built.

Tornado chasers study a dark sky with a perfectly arced rainbow. Storm chasers drive a fine line between staying safe and getting close enough to a twister to gather the data they're after.

A damaged mobile home after a tornado. The interior of a big tornado can reach speeds of 200 mph, enough to flatten anything in its path.

These three photos track the formation of a tornado funnel in Kansas. On the Great Plains, conditions are perfect for tornadoes. More than a thousand a year form there as moist air from the Gulf of Mexico meets dry air from the Rocky Mountains.