Endosymbiosis describes a mutually beneficial relationship between species in which one party lives inside the other. In the oxygen-free microenvironment of a termite's gut live hundreds of species that exist nowhere else on the planet. These microbes enable their insect host to digest the wood it infamously devours. Darkfield microscopy, 100-400x magnification. This episode was made in collaboration with Jared Leadbetter PhD at the California Institute of Technology.