Turkey, tomato, and Swiss on a bed of romaine lettuce sandwiched between two slices of sourdough.

Classic, but oh no!

What's this? Mold? Ugh.

But look, good news, the mold's only on part of the bread so I could just cut that away and be fine, right?

There's no such thing as a clean part of moldy bread.

That's because mold is a fungus like mushrooms.

The caps on the surface are easy enough to spot, but there's a vast network of subterranean roots called hyphae that you can't see.

So let's take another look at that bread of yours.

Ugh, disgusting.

Well, maybe you can just grab another piece from the same loaf.

Well, that's not such a good idea, either.

Because by the time the mold sprouts its fuzzy head, what you're really seeing is the reproductive part of the mold called sporangiums.

Each sporangium releases tens of thousands of spores, so even though you can't see it, that entire loaf could be teeming with fungus.

But it seems like such a waste to just throw it out.

After all, you eat mold on purpose all the time like the mold that goes into making cheese, soy sauce, and even life-saving antibiotics like penicillin.

Eating a little bit on your bread can't be that bad, right?

Well, ultimately, it's a gamble.

Just like eating a wild mushroom.

Many are fine, but some can be deadly.

Mold is the same way.

There are thousands of different species of mold, many of which are harmless to humans.

But since so many types can sprout up on food, it's nearly impossible to know if what you're eating is safe.

Cladosporium, for example, can sometimes trigger allergies but is generally harmless, whereas other molds like Penicillium Crustosum produce harmful poisons called Mycotoxins.

An elderly couple in 2005, for example, was admitted to the hospital after eating a can of soup contaminated with this kind of mold.

They had severe muscle tremors but eventually recovered.

But other molds, like Rhizopus Stolonifer, can have permanent effects, and you might recognize this mold since it commonly grows on bread.

Blue green with black splotches and super fuzzy.

In rare cases, it can prompt a deadly infection called Zygomycosis, which causes your blood to clot and can ultimately starve your cells of oxygen to the point that they die.

And it's not like bacteria, where a little heat will eliminate the threat, because high temperatures won't break down the Mycotoxins.

And since you have no clue which one you're about to put in your mouth, ask yourself: is it really worth the risk?