The quality is not so great - it was dark, after all. But tornado chasers at tornadolive.com managed to capture several glimpses - in lightning flashes - of the huge, F-5 "wedge" tornado that leveled Greensburg, Kan. over the weekend. And their reactions to what they were witnessing convey something of the awe and fear they felt in the face of one of the most powerful tornados to strike the U.S. in years. Click here.

For more on the Fujita Scale of tornado intensity, click here. Here's a list of the F-5 twisters that have struck the U.S., the most recent in 1999. And here's a list of the top-10 killer tornadoes in our past.

The miraculous thing about this F-5 tornado in Greensburg was that it killed so few people - fewer than 10 in a community of 1,500. Modern forecasting and warning systems have reduced the number of tornado deaths in recent years, despite increasing populations and exposure. But the devastation in Greensburg was enormous. Here are some still photos.