“Spontaneous fermentation” sounds like the worst two-word Instagram bio you’ve ever read. Or something terrible that would show up in an online dating profile. “Hey. I’m 23. Just moved to the city. Can’t wait to spontaneously ferment with some interesting humans!” Nope. I’m good. Thanks.

But spontaneous fermentation, unlike the world of online dating, is something you should understand because the coolest beers, ciders, wines, and liquors right now are being made through this process, delivering unexpected flavors that range from ripe raspberries to fresh cane sugar to tart lemon to the juiciest of melons. “We’ve seen a huge increase in breweries starting up legitimate spontaneous programs,” says Joshua Van Horn, owner of Brooklyn’s Gold Star Beer Counter. “Seeing more breweries catching on gives me hope that we will see many more being released. We try our hardest to get those beers in our door.”

Dude, that’s great. Sounds rad. I love cool beverages. So down for them. But what the hell is spontaneous fermentation? Can you explain it to me before you…say it again?

Yes. Totally. Well, I’ll say it one more time, because I have to. Spontaneous fermentation is what happens when a brewer, winemaker, or distiller leaves the inoculation (the moment when yeast and bacteria come in contact with the liquid) up to whatever organisms happen to be in the air or on the fruit that they are fermenting. This is different from the process of most mass-produced booze, where industrialized, controlled yeast strains or blends are deliberately poured into a sugary liquid. Brewers don’t know exactly what’s ending up in the beer or wine or cider. All they know is that the fermentation will be, as advertised, spontaneous.

This fermentation method is nothing new. In fact, it’s the oldest method of booze making there is. Before humans knew what yeast, bacteria, or ride-sharing apps were, they made party liquids by letting fruit juice or sugary water hang around in big jugs until something happened. It wasn’t until the 17th century, when a Dutch scientist named Antonie van Leeuwenhoek (great name, btw) observed microorganisms under a magnifying lens that we even knew that these little bugs existed. And it wasn’t until Louis Pasteur actually discovered how yeast works in 1859 that we realized the role it played in fermentation.