Victoria, a 2-year-old rat, sniffs for TNT, sticking her nose high in the air to indicate she's found some. She works her way down a 10-meter line with a handler on either end, and is able to detect the presence of TNT at a distance of approximately half a yard. Michael Sullivan for NPR hide caption

itoggle caption Michael Sullivan for NPR

In the study, muscle cells were injected into the cell-free "scaffolding" of a rat limb, which provided shape and structure onto which regenerated tissue could grow. Bernhard Jank, MD/Ott Laboratory, Massachusetts General Hospital Center for Regenerative Medicine hide caption

itoggle caption Bernhard Jank, MD/Ott Laboratory, Massachusetts General Hospital Center for Regenerative Medicine

Gerbils are harmless... Right? Peter Knight/Flickr hide caption

itoggle caption Peter Knight/Flickr

Who, me? The Asian relative of this domestic gerbil is a well-known host to the bacteria that cause plague. Valentina Storti/Flickr hide caption

itoggle caption Valentina Storti/Flickr

New Yorkers can take city-run classes to learn how to make their homes and businesses less attractive to these guys. Ludovic Bertron/Flickr hide caption

itoggle caption Ludovic Bertron/Flickr

Rats aren't only problem in Tehran. These were running free over the weekend in Luton, England. Barcroft Media/Barcroft Media /Landov hide caption

itoggle caption Barcroft Media/Barcroft Media /Landov