There are 6,200 known invasive species in the United States, and scientists are scrambling to stop their unique paths of destruction, which can take a huge toll on regional economies and ecosystems. To effectively combat an invader, scientists must know the organism inside and out: What does it eat? How does it reproduce? What was its environment like in its native home? There are many questions, but just one right answer might yield a weakness in the enemy. In this entry in the Scientists in the Field series, Sneed B. Collard III introduces readers to some of the most brilliant minds, and promising advances, in the war against invasive species.