The bacterium Vibrio fischeri is a squid terraformer. Although it can live independently in seawater, it also colonises the body of the adorable Hawaiian bobtail squid. The squid nourishes the bacteria with nutrients and the bacteria, in turn, act as an invisibility cloak. They produce a dim light that matches the moonlight shining down from above, masking the squid’s silhouette from predators watching from below. With its light-emitting microbes, the squid becomes less visible.

Inside its egg, an embryonic squid is sheltered in a sterile bubble. When it hatches, it starts pumping seawater into its body, bringing a flood of bacteria into contact with a special light organ. Among these teeming hordes is V.fischeri. It gathers in the layer