When my mom got home from work, she would ask me how school was. If I told the truth, she would hold me and comfort me, encouraging me that this was temporary, that life would get better. But most days I would lie and tell her that school was fine. I didn’t want my hurt to travel through to her. On those days, I would go into my room and pull the pink sticker book out from my bookcase, and I would scratch the stickers, close my eyes, and inhale as deeply as I possibly could.

I had all the hits: Garfield eating chocolate, the lawn mower that smelled like grass, the taco that smelled like tacos. But I particularly loved the fruits—the cloyingly and otherworldly sweet distillations of raspberry and strawberry and banana. God, I loved scratch ’n’ sniff bananas. They didn’t smell like bananas, of course. They smelled like the Platonic ideal of bananas. If real bananas were a note played on a home piano, scratch ’n’ sniff bananas were that same note played on a church’s pipe organ.

Anyway, the weird part is not that I collected scratch ’n’ sniff stickers until I was a teenager. The weird part is, I still have that sticker album. And the stickers, when scratched, still erupt with scent.

Scratch ’n’ sniff stickers are created by a process called microencapsulation, which was originally developed in the 1960s for carbonless copy paper. When you fill out a white paper form and your pen imprints upon the pink and yellow sheets below, that’s microencapsulation at work. Tiny droplets of liquid are encapsulated by a coating that protects those droplets until something decapsulates them. In copy paper, the pressure of a pen releases encapsulated ink. In scratch ’n’ sniff stickers, scratching breaks open microcapsules containing scented oils.

Microencapsulation is used for all kinds of things these days—including time-released medication—and it has proven a useful technology in part because, depending on the coating used, microcapsules can last a while.

How long? Well, I know for a fact that scratch ’n’ sniff stickers can survive for at least thirty-four years, because I just scratched a garbage can sticker I got when I was seven, and it still smells. Not like garbage, exactly, but like something.

The longevity of microcapsules offers a tantalizing possibility: that a smell might disappear from our world before the microencapsulated version of that smell disappears. The last time anyone smells a banana, it might be via a scratch ’n’ sniff sticker, or some futuristic version of one.

This all makes me wonder what smells I’ve already missed out on. When thinking about the past, we tend to focus on the awful smells, which were apparently legion. Ancient writers often showcase an acute awareness of disgusting odors—the Roman poet Martial compares one person’s scent to “a chicken putrefying in an aborted egg” and “a billy goat fresh from making love.”

But there must also have been wonderful smells, many of which are gone now. Or at least gone for now. It’s conceivable that they’ll be back with us in scratch ’n’ sniff form someday: In 2019, scientists at Harvard used DNA samples of an extinct species of Hawaiian mountain hibiscus to reconstitute the smell of its flower. But there’s no real way to judge the scent’s accuracy, since its antecedent is gone forever.