One of the things that makes smell so powerful, of course, is its connection to memory. Helen Keller wrote that smell is “a potent wizard that transports us across a thousand miles and all the years we have lived.” The scent of artificial “Spring Rain” takes me back to an Alabama dorm room in 1993. The smell of actual spring rain, meanwhile, returns me to the drenching thunderstorms of my childhood in Central Florida.

Smell’s radical specificity is part of what connects it so particularly to memory; it’s also part of why imitation is so difficult, even when it comes to artificial odors. The scent of Chanel No. 5, for instance, is not patented, and doesn’t need to be, because no one can re-create it. But I think there’s something else at play with smells that try to mimic nature, which is that nothing in the real world ever smells quite like we imagine it should. Actual spring rain, for instance, seems like it ought to smell at once moist and crisp, like the artificial scent does. But in fact, springtime rain smells earthy and acidic.

Humans, meanwhile, smell like the exhalations of the bacteria that colonize us, a fact we go to extraordinary lengths to conceal, not only via soap and perfume, but also in how we collectively imagine the human scent. If you had an artificial intelligence read every novel ever written and then, based on those stories, guess the human odor, the AI would be spectacularly wrong. In our stories, people smell like vanilla, lavender, and sandalwood. The AI would presume we all smell not like the slowly decaying organic matter we are, but instead like newly mown grass and orange blossoms.

Which, incidentally, were two of the scratch ’n’ sniff sticker scents from my childhood. Scratch ’n’ sniff stickers were wildly popular in the 1980s, and I maintained a collection of them in a large pink sticker book. The stickers fascinated me—if you scratched or rubbed them, scent erupted without explanation. Like most virtual scents, scratch ’n’ sniff smells tend to be rather imperfect simulacrums, which is why the stickers generally depicted the scent they were going for. The pizza-scented stickers were usually slices of pizza, and so on. But they really did smell—often quite overpoweringly.

The smells best captured by scratch ’n’ sniff tend to be either aggressively artificial—cotton candy, for instance—or else straightforwardly chemical. A rotten eggsy odor is added to natural gas so that humans can smell a gas leak, and in 1987, the Baltimore Gas and Electric Company sent out scratch ’n’ sniff cards to their customers that mimicked the odor so effectively that several hundred people called the fire department to report leaks. The cards were soon discontinued.

By the time I was ten or eleven, everyone had moved on from sticker collecting—everyone, that is, except for me. Even in middle school, I continued to surreptitiously collect stickers, especially scratch ’n’ sniff ones, because they took me back to a time and place that felt safer. In sixth grade, I had one class in a trailer each day. Because of some scheduling error, the teacher of that class had to walk across the entire school to get to the trailer, which meant that for about five minutes, we students were all on our own. Many days, a group of kids would throw me to the ground and then grab me by my limbs and pull on me as hard as they could. They called this “the abominable snowman.” Other times, garbage was poured on my head as I sat at my desk. Aside from the physical pain, it made me feel small and powerless. But I didn’t really resist it, because many days it was the only time I had any social interaction. Even when there was wet garbage on my head, I tried to laugh, like I was in on the joke.