Being able to see what is going on inside test animals would allow researchers to have an immediate analysis of the effects of experimental compounds or treatments. In some cases this is possible, for example with the nematode C. elegans, which is transparent. Unfortunately, other animals keep their internal processes concealed. Xenogen Corp. has developed a system to remove that barrier and permit direct visualization of cells and other biological events within living mammals.

Xenogen's approach is to monitor light of certain wavelengths emitted from inside an animal. "We generate an internal source of biochemical light, and use special camera technology to capture that," said Co-founder and President Pamela Contag. The result, termed "molecular biophotonics," depends upon reporter genes encoding luciferase, the protein that gives fireflies and some bacteria their signature bioluminescence.