Although comb jellies seem to be little more than tennis ball-sized blobs in the sea, these organisms are relatively sophisticated in how they use light. The creatures flash a blue-green light at predators, for example, possibly to startle them. Researchers studying the genome of the comb jelly, also known as a ctenophore, have discovered that the bioluminescent creatures pack in 10 proteins for generating light. They have other proteins called opsins that detect light, even though comb jellies lack eyes. It's not clear what these opsins do in this animal. The genome is the first to be sequenced from a bioluminescent animal. Because ctenophores appear to sit at the base of the animal tree of life, the findings suggest that light-generating and sensing proteins evolved at the same time as multicellularity. Such proteins may have given rise to the diversity of light-sensing molecules seen in animals today, such as in the rods and cones in human eyes. And studying them, the researchers say, could lead to new insights into the origin of eyes and therapies for treating sight disorders.