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.

In fact, while I’ve been making distinctions between natural scents and artificial ones, at this point in our planet’s story, many purportedly natural scents are already shaped by human intervention, including the banana. In the U.S. at least, there is only one banana cultivar in most grocery stories, the Cavendish banana, which didn’t exist two hundred years ago and was not widely distributed until the 1950s.

I remember the smell of rain as acidic in part because rain in my childhood actually was more acidic than contemporary rain. Humans were pumping more sulfur dioxide into the atmosphere in the 1980s than they are today, which affects the pH of rain. In my part of the world, rain is still more acidic than it would be without human emissions, so I’m not even sure that I know the smell of “natural” rain.

The challenge for scratch ’n’ sniff sticker makers isn’t, in the end, to mimic the natural world, which doesn’t really exist as a thing separate from humanity. The challenge is to imagine what combination of smells will make humans remember the smell of bananas, or ocean mist, or freshly mown grass. I wouldn’t bet against us finding a way to artificialize scent effectively—God knows we’ve artificialized much else. But we haven’t succeeded yet. When I open that ancient sticker book and scratch at the yellowing stickers curling at the edges, what I smell most is not pizza or chocolate, but my childhood.

I give scratch ’n’ sniff stickers three and a half stars.

DIET DR PEPPER

THE STORY OF DR PEPPER BEGINS IN 1885, in Waco, Texas, where a pharmacist named Charles Alderton combined twenty-three syrup flavors to create a new kind of carbonated drink. Notably, Alderton sold the recipe for Dr Pepper after a few years because he wanted to pursue his passion, pharmaceutical chemistry. He worked at the drug company Eli Lilly before going back to his hometown to head up the laboratory at the Waco Drug Company.*

Alderton’s soda probably would’ve remained a Texas-only phenomenon, eventually disappearing like so many other local soda flavors—the opera bouquet, the swizzle fizz, the almond sponge—had it not been for the dogged determination of Woodrow Wilson Clements, who preferred to be called “Foots,” a nickname he picked up in high school due to his oddly shaped toes. Foots, the youngest of eight children, grew up in the tiny Alabama town of Windham Springs. He got a football scholarship at the University of Alabama, where he was teammates with Bear Bryant.*

In 1935, when Foots was a senior in college, he started working as a Dr Pepper salesman. He retired fifty-one years later as CEO of a soft drink company worth over $400 million. By 2020, the Keurig Dr Pepper corporation, which owns, among many other brands, 7UP, RC Cola, and four different kinds of root beer, is valued at over $40 billion. Almost all of its products are some form of sweetened and/or caffeinated water.

Foots Clements succeeded because he understood precisely what made Dr Pepper significant. “I’ve always maintained,” he said, “you cannot tell anyone what Dr Pepper tastes like because it’s so different. It’s not an apple; it’s not an orange; it’s not a strawberry; it’s not a root beer; it’s not even a cola.” Cola, after all, is derived from kola nuts and vanilla, two real-world flavors. Sprite has that lemon-lime taste. Purple soda is ostensibly grape-flavored. But Dr Pepper has no natural-world analogue.

In fact, U.S. trademark courts have tackled this issue, categorizing Dr Pepper and its knockoffs as “pepper sodas,” even though they contain no pepper, and the “pepper” in Dr Pepper refers not to the spice but either to someone’s actual name or else to pep, the feeling that Dr* Pepper supposedly fills you with. It’s the only category of soda not named for what it tastes like, which to my mind is precisely why Dr Pepper marks such an interesting and important moment in human history. It was an artificial drink that didn’t taste like anything. It wasn’t like an orange but better, or like a lime but sweet. In an interview, Charles Alderton once said that he wanted to create a soda that tasted like the soda fountain in Waco smelled—all those artificial flavors swirling together in the air. Dr Pepper is, in its very conception, unnatural. The creation of a chemist.

* * *

The first zero-calorie version of Dr Pepper was released in 1962. This initial “Dietetic Dr Pepper” was a failure, but Diet Dr Pepper became a huge success when it was reformulated in 1991 with a new artificial sweetener, aspartame. It also relaunched with a new advertising slogan. Diet Dr Pepper: It tastes more like regular Dr Pepper. Which it really does. Coke and Diet Coke are barely recognizable as relatives. If Coke is a golden eagle, Diet Coke is a hummingbird. But Dr Pepper and Diet Dr Pepper taste like each other, which is especially interesting since, as Foots Clements pointed out, neither of them tastes like anything else.

Now, many people find the artificiality of Diet Dr Pepper revolting. You often hear people say, “There are so many chemicals in it.” Of course, there are also lots of chemicals in wine, or coffee, or air. The underlying concern, though, is a sensible one: Diet Dr Pepper is just so profoundly artificial. But that’s why I love it. Diet Dr Pepper allows me to enjoy a relatively safe taste that was engineered for me. When I drink it, I think of the kids at that soda fountain in Waco, Texas, most of whom rarely knew the pleasures of an ice-cold drink of any kind, and how totally enjoyable those first Dr Peppers must’ve been.

Each time I drink Diet Dr Pepper, I am newly astonished. Look at what humans can do! They can make ice-cold, sugary-sweet, zero-calorie soda that tastes like everything and also like nothing. I don’t labor under the delusion that Diet Dr Pepper is good for me, but, in moderation, it also probably isn’t bad for me. Drinking too much Diet Dr Pepper can be bad for your teeth and may increase other health risks. But as Dr. Aaron Carroll puts it in his book The Bad Food Bible, “There’s a potential—and, likely, very real—harm from consuming added sugar. There is likely none from artificial sweeteners.”