Host Defense is built on Paul Stamets' visionary research into the power and potential of mushrooms, especially mushroom mycelium, the root-like structures found growing below ground. The power of Host Defense comes from the discovery that the mycelium is the immune system of the mushroom. Just as mycelium helps to support the immune system of humans, it also supports the health and immunity of the natural habitats where it grows. Mushroom mycelium is a cellular bridge connecting bees, trees, bears, plants and humans to the ecosystems in which they live. Host Defense's mission to build a healthier world with the power of mushrooms.