Mold

There are over 300,000 types of mold; they are thread-like, multicellular fungi organisms that reproduce via spores. Mold prospers in warm, humid environments. By all accounts they look very similar to a plant under a microscope; it has roots, a stalk, and little spores resembling flowers.

Depending on the mold, it could be extremely dangerous to ingest. Mycotoxins are produced by molds present on nut crops and in grain, but they could also come from molds growing on fruits, like apples. Another type of toxin, called aflatoxins, can even cause death. Some people are dangerously allergic to certain types of mold. Ironically, most molds present on bread aren't inherently poisonous, but they hasten the decomposition of the bread itself.

Molds are everywhere, and it's a fact of life that our food will always contain the spores. The key is to prevent its growth. Contrary to popular belief, cutting off the moldy parts of food will not rid it of the roots and spores; it's still dangerous to eat. Cutting off the moldy parts also doesn't factor in the bacterial growth that occurs in tandem.

Not all mold is evil, however. Molds in their natural environment play a key role in decomposition of organic material. The mold Penicillium is extremely important for the production of antibiotics such as penicillin, the world's first man-made antibiotic. Certain molds are also tamed for the ripening of cheese.

https://www.webmd.com/diet/what-to-know-mold-food
https://science.jrank.org/pages/4396/Mold.html