When we think of mushrooms we usually think of the small white ones we buy from the store to cook. We certainly don't think of mushrooms actively killing the things around them. However, fungus Armillaria Ostoyae was found to be killing huge swaths of conifer trees in the Oregon Blue Mountains, by causing a root disease. And more shocking, it was revealed that it was all about a single individual, as big as 800 soccer fields! The biggest living organism in the world! It's aged at least 2,400 years and, although it spreads out in the underground as a shoestring fungus, it appears in the surface as inoffensive and eatable honey mushrooms.