The Armillaria ostoyae, more commonly known as the honey mushroom, began as a microscopic spore and has been constantly growing and taking over eastern Oregon's Malheur National Forest for the past 2,400 years!
This mushroom is the LARGEST LIVING ORGANISM EVER FOUND. It spans 2,200 acres - which is an area equivalent to 1,665 football fields!!! As it grows, it covers the forest and kills trees!
For more info, check out the news story at ABC News.
Here's a barely relevant video. The internet was weird before YouTube.