On the mountaintop glaciers of the Pacific Northwest lives a mysterious, and often, overlooked creature. They're small, thread-like worms that wiggle through snow and ice. That's right, ice worms! NPR science correspondent Nell Greenfieldboyce talks to Emily about how they survive in an extreme environment and why scientists don't understand some of the most basic facts about them. For more of Nell's reporting, you can follow her on Twitter @nell_sci_NPR. You can follow Emily @emilykwong1234. Email the show with suggestions or thoughts at ShortWave@NPR.org.