The hot springs and geysers of Yellowstone were among the first places that researchers discovered single-celled microorganisms known as Archaea; they flourish in its hot, sulfuric pools. The park not only harbors extremophiles, it is a home for many iconic American species, from bald eagles to buffalo. The alpine landscape is dotted with broadleaf aspen trees, which anchor the rivers and keep soil from eroding into them. While the animals are not as plentiful as they were in the 1800s, massive herds of elk and buffalo famously roam and graze.