Fungi range from single-celled to the largest multicellular organisms. The largest known organism on earth is a fungus living in the Malheur National Forest in eastern Oregon. At least 2,400 years old its mycelium covers 2,200 acres (nearly 3 and a half square miles)!
A typical multicellular fungus is comprised of tiny threads called hyphae. These threads grow into a tangle of filaments forming a mat (mycelium). The mycelium is the feeding structure for the fungus but also increases soil’s water infiltration and holding capacity.