It’s hard to overestimate the importance of fungi—and easy to understate how little we know about them. Scientists have described a little over 100,000 different species, while estimating that there may be as many as 3.8 million.

Fungi do many unseen and unglamorous tasks. They break down countless amounts of detritus and dead things, and they cycle nutrients throughout the environment, without which the world would cease to function. They also make plant life possible: Vast webs of fungi stretch through soil, transferring chemical signals, food, and water. Not to mention their more fun roles, like fermentation, which creates alcohol, leavened bread, and much more.

Much of the distant history of fungi remains a mystery, however. While they branched off from