![](https://paw.princeton.edu/sites/default/files/styles/feature_image/public/images/content/Brainbow.jpg?itok=fHVjDqBL)
![](https://paw.princeton.edu/sites/default/files/styles/feature_image/public/images/content/Brainbow.jpg?itok=fHVjDqBL)
Genetically engineered viruses leave colorful tracks as they travel through a rat’s brain and help map the degree of connection in neurons involved in blood-pressure regulation. The image was created by molecular biology professor Lynn Enquist and J. Patrick Card, a professor at the University of Pittsburgh.