A blue whale? They are indeed the largest animal that has ever lived...can grow up to 108 feet long and 172 metric tons...
A giant sequoia? General Sherman, at 274 ft high and 108 ft in circumference, contains 52,584 cubic feet of wood...
So that's it, right? Plants and animals?
Oh wait, there's bacteria and archaea and fungi, too. Of course bacteria and archaea are microscopically small, but there's no way that there's a mushroom bigger than a giant sequoia, right?
As epic as that would be, the answer is no. However, what you see when mushroom hunting is just the ephemeral fruiting body, the distributor of spores, and far less than the proverbial tip of the iceberg. The bulk of a fungus is actually underground, in a dense network of cells called a mycelium. There are a few really cool things about mycelium: 1)it's made up of cells called hyphae, which are all pretty much identical, 2)strands of these hyphae are only one cell thick, 3)hyphal growth is directed by organelles called "spitzenkörper" (which is just a really cool word) and 4)the cobweb-like structure of mycelium can be so dense that a single cubic inch of soil can contain up to eight miles of hyphae!
Since the majority of a fungus is a spongy mesh of single-celled tubes underground, it can absorb nutrients and water directly from its surroundings, it's pretty well protected, and it doesn't need to hold itself up. These factors should allow it to grow pretty much indefinitely... and it does, in some cases.
Up in the Malheur National Forest of eastern Oregon, there's a giant network of genetically identical mycelium that spans... 8.9 square kilometers. Almost three and a half square miles. Not only that, but it's estimated to be 2400 years old. Dude.
But let's take that density thing and run with it. Eight miles of hyphae in a cubic inch of soil means that there's a lot of criss-crossing fibers, hundreds or maybe thousands of layers thick, forming a redundant, resilient network, like kevlar... or fiberglass insulation...
Hey, what if we could do something with that? What if we grew a bunch of super-dense mycelium into forms that we could use, and then dried it, so that we'd have a really tough custom-shaped material for, say, structural strength, or insulation, or packaging? We could build things out of it, or keep our houses warm, or ship fragile things in it... and since it's made of mushrooms, we could just throw it away or compost it, and it would be completely biodegradable!
Well, lucky for us, such a thing does exist. A bunch of
To make this kind of fungal Styrofoam, they take byproducts of agricultural crops, such as cotton burrs or buckwheat hulls, load them up with fungal spores and fungus food, and let 'em grow. After a few weeks, the hyphae have surrounded and consumed the agricultural byproducts, forming that dense mycelium. As it grows, the mycelium fills out whatever mold it's started in, whether that's in the form of a brick, a large flat panel, or a custom shape that perfectly fits whatever product you need to carefully package.
Once it has grown to the proper size and shape, they cook it to render it "biologically inert," which is a fancy engineer way of saying "dead." Depending on the proportion of ag byproducts and fungal spores they use, they can change the properties of the "fungoam" (I just made that up) to make it harder or softer. Grown in the right proportions, they can actually make this stuff stronger than concrete, but a whole lot lighter. Plus, it's mold- and moisture-resistant, is a better thermal and vibration insulator than Styrofoam, and it's fireproof!
This stuff is super eco-friendly, too. Not only is it made from living things that require no light and only room-temperature heat (requiring one tenth of the energy of synthetic foam), but
"The raw material inputs of EcoCradle™ are selected based on regionally available agricultural by-products. So a factory in Texas or China might use cotton seed hulls, and a factory in Virginia or Spain might use rice husks and soybean hulls. By manufacturing regionally, and using local feedstocks, we aim to minimize the trucking of raw and finished materials." (http://www.ecovativedesign.com)Since it's made of fungus instead of synthetic materials, after you're done with it, you can just throw it in your compost and return it to the environment whence it came, returning its nutrients to the soil to fuel the next generation of fungus.
According to Ecovative Design, EcoCradle™ is going to be protecting a soon to be shipped unnamed product, and their website shows packaging for some cylindrical device, but presumably, with a large enough mold, they could make anything, like entire buildings! Or Paul Bunyan statues! Or life-size models of General Sherman!