The Hawaiian bobtail squid and its resident bacterium, Vibrio fischeri, have a powerful and still somewhat mysterious symbiotic relationship. The luminescent bacteria populate a small pouch on the squid’s underside called the light organ, and provide a sort of “Klingon cloaking device.” They produce light at night to offset the squid’s shadow and hide it from predators when it approaches the ocean’s surface to feed. At the University of Wisconsin-Madison, microbiologist Margaret McFall-Ngai studies this unusual relationship. An understanding of these creatures’ rhythms could lead to new ways to treat disease. She is also studying how the squid and bacteria communicate, so they don’t harm each other.