Encounter hundreds of species of microbe that exist nowhere else on the planet outside of a termite's gut. These microbes enable their termite host to digest the wood it infamously devours. The termite and these microbes share what is called an obligate endosymbiotic relationship. That is, neither could survive without the other's help, and one species lives inside the other. If you loathe termites, remember that overall, termites are absolutely essential to recycling dead plant material. Only 10% of the 3000 species of termite on the planet cause damage to human habitation. Without them, and by extension without these invisible microbes, the surface of the Earth would be buried under miles of rotting plant material.