The Australian stinging tree (Dendrocnide moroides) is a plant that many people avoid at all costs. The tree, which is a member of the nettle family, is covered in thin silicon needles laced with one of nature's most excruciating toxins, a compound called moroidin. "It's notorious for causing extreme pain, which lingers for a very long time," said Whitehead Institute Member Jing-Ke Weng.