"We were trying to figure out how to do it in a way that would recreate a bunch of different environments in an immersive experience and cover it all," says John Sparks, AMNH curator of ichthyology, "[to] expose people to the diversity of bioluminescence across the tree of life." Just as a variety of creatures use bioluminescence, they use it for a variety of reasons. Some use it to lure prey, or to signal potential mates. Other strategies are a bit cleverer. Sparks says some species, such as the dragonfish and hatchetfish, use "counterillumination" to hide. That is, the light they generate on their undersides is fine-tuned to match the amount of sunlight that pierces down to a particular depth, camouflaging them. The cookiecutter shark, which Sparks wasnt able to include in the exhibit, uses bioluminescence to appear smaller than it is, luring in unsuspecting life forms who think theyre going to get an easy meal and that promptly become the meal.