This article originally appeared in the December 2016 issue of ELLE.

1889. The Eiffel Tower was inaugurated, its 984 feet of wrought-iron latticework making it the tallest structure in the world. Charlie Chaplin and Adolf Hitler were born, Vincent van Gogh painted The Starry Night, and American journalist Nellie Bly circumnavigated the world in a record 72 days, picking up a pet monkey along the way. Change was in the air, literally: The year also marked the debut of Guerlain's Jicky, the first perfume to combine both synthetic and natural notes to create an abstract olfactory effect that was simultaneously spicy, strange, and striking. Before this, if you had pressed your nose to a woman's wrist or a man's lapel, you would have smelled only flowers.

Jicky contained two relatively inexpensive and versatile synthetics—coumarin, a substance found in tonka beans that smells of freshly mown hay, which had been synthesized by chemist William Henry Perkin in 1868; and vanillin, a vanilla-scented molecule first successfully derived from pine bark in 1874—and was considered the first truly modern fragrance. It ushered in an era in which perfumers were no longer compelled to work only with traditionally extracted botanicals and unsavory animal excretions such as musk, ambergris, and civet. Around the turn of the century, a flurry of innovative olfactory chemicals hit the market—including ionones, which simulate the soft scent of violets; creamy-smelling lactones; and synthetic musk, which was discovered accidentally by a chemist trying to make explosives. With these manufactured molecules suddenly available in perfumers' tool kits, fragrances essentially went from analog to digital, from black-and-white to color.

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Courtesy of Guerlain//Getty Images
Guerlain\'s landmark Jicky in its original 1889 bottle; Shalimar, launched in 1925, gets its distinctive heady sweetness from an overdose of ethyl vanillin.

"Synthetics are what made modern perfumery possible," says scent maker Rodrigo Flores-Roux, who has created fragrances for Calvin Klein, Tom Ford, and niche brand Arquiste, among many others. "Historically, it's been the application of something never used before or an overdose of an ingredient that has made a perfume stand the test of time, and in almost every case, like the famous aldehydes in Chanel No. 5, it was a synthetic material that did this."

In the fragrance world, entire eras have been defined by the discovery of new molecules. Men's colognes were forever changed after the first use of Hedione—a luminous, jasminelike note, later proven to actually activate pheromone receptors in women's brains—in Christian Dior's Eau Sauvage in 1966. Thierry Mugler's heady Angel, which owes its cotton-candy sweetness to ethyl maltol, created a new fragrance category, the "oriental gourmand," when it launched in 1992. And the clean, ozonic scents that dominated the late '90s were all based on a watery, melony molecule called Calone, a signature note in Issey Miyake's iconic L'Eau d'Issey.

"People tend to think that perfumes are made from three or four things, like rose, patchouli, and sandalwood, because those are the main notes," Flores-Roux says, "but a perfume on average has between 40 and 60 ingredients. And generally speaking, synthetics are present at about 70 percent and naturals at 30 percent." Despite their significance and ubiquity, however, the chemicals that shape our beloved scents have long been shrouded in mystery—and even regarded with a degree of suspicion: Are they necessary? Are they safe? Only recently—somewhat ironically, in these green-minded times—a new generation of perfumers have become outspoken about their use of and appreciation for synthetics, just as fragrance brands have begun to emerge that proudly broadcast lab-concocted notes as their raison d'être.

With these manufactured molecules suddenly available, fragrances essentially went from analog to digital, from black-and-white to color.

"We've been using synthetics for 150 years, and for 150 years no one has talked about it," says Cartier perfumer Mathilde Laurent. "I find that to be such a lack of courage." Contrary to popular belief, says Arquiste founder Carlos Huber, engineered ingredients are not inherently inferior to botanical extracts. "That's a very misinformed idea. Quality is quality, number one. There are bad synthetics and there are good synthetics, just as there are good naturals and bad naturals. It's all about how they're used."

Synthetic aroma molecules are mostly ginned up in the top secret labs of the handful of corporations responsible for manufacturing the majority of perfumes sold today—Symrise, Firmenich, International Flavors & Fragrances (IFF), Givaudan, and Takasago—each of which employs a battery of PhD-wielding R&D scientists whose job it is to disassemble and reassemble chemical bonds; break apart clusters of hydrogen, carbon, nitrogen, and oxygen (the main building blocks of all molecules, whether made by Mother Nature or in a test tube); and reconstruct them in new configurations. Sometimes they know precisely what they're looking for—a more radiant citrus, for example, or a particularly dark, earthy wood—but in many instances they are simply experimenting to see what lucky results may occur. "Columbus left to discover a route to India but ended up in America," says Anubhav Narula, research director for fragrance ingredients at IFF. "A scientist may design a molecule to make a rose but end up with a jasmine."

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From Right: French advertisement from Lancome perfumes, 1958 ; Crimson of the Orient, perfume by Roger and Gallet, 1930; advertisement for Vol de Nuit perfume by Guerlain, published in french magazine, in the early 60\'s.

In general, these laboratory creations take three forms. The first are nature-identical, which means that they are engineered versions of the exact same molecules that exist in nature (everything we smell, whether a blooming hyacinth or a pile of garbage, is comprised of thousands of scent molecules). The second begin with a natural raw material that is in some way manipulated into something else (vetiveryl acetate, a chemically transformed vetiver that smells sweeter than the actual plant, is a common example). And the third are man-made from start to finish. When a fragrance house devises a new molecule—roughly three or four are introduced by each company every year—it becomes what is called a "captive," a proprietary ingredient that can only be used by perfumers who work for that company until the patent expires. These exclusive creations are valuable assets, providing an edge over other perfumers who may be seeking the same commission: If noses from both IFF and Givaudan are submitting trials for a new Marc Jacobs eau, for example, the one with the most novel ingredient may well win.

The individual aldehydes in Chanel No. 5 burst off the paper with a sparkling vivacity that, if rendered in cartoon form, would be depicted by a surge of stars or tiny suns shooting up my nostrils.

When I visit the Manhattan headquarters of IFF, senior fine fragrance perfumer Yves Cassar ushers me into the fragrance lab, where hundreds of small brown-glass bottles crowd glass shelves. He waves a series of blotters under my nose: Cashmeran, which gives Donna Karan's Cashmere Mist its seductive smoothness, is woody, soft, almost undetectable; Galaxolide, a synthetic musk created by IFF chemists in 1965 that became extremely popular after its use in Jōvan Musk in 1973, is so velvety and animalic it's like smelling warm fur; the individual aldehydes in Chanel No. 5 burst off the paper with a sparkling vivacity that, if rendered in cartoon form, would be depicted by a surge of stars or tiny suns shooting up my nostrils.

Raymond Matts, who teaches fragrance courses at New York's Pratt Institute and has his own line of perfumes, Aura de Parfum, says that lab-made notes allow him to bring "texture" to his creations. "If I want to convey sensuality, the feeling of skin or a soft caress that gives you goose bumps, how do I do that? I use synthetics." They can even be used to heighten the effects of some naturals, making them smell more, well, natural. Rose oil, for example, doesn't really smell like roses—it conveys bitter earthiness rather than the luscious, swoony scent we get when we smell the bloom in the air. In order to re-create a true nose-to-petal effect, a perfumer often has to employ a little sleight of hand.

"I prefer to work with flowers I reconstitute myself," Laurent says. "It's not being a perfumer to make jasmine with jasmine absolute. I think it's more interesting to create gardenia without gardenia. It's like the Impressionists, who wanted to paint the emotion of being in nature. It's the job of the perfumer to give the feeling of nature without the presence of nature."

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Courtesy of Chanel
A 1921 ad for Chanel No. 5

One misconception about manufactured notes is that they're cheap, and therefore more likely to be used in great quantities in, say, a drugstore spritz than in a Tom Ford eau. This isn't necessarily the case, says Firmenich senior perfumer Frank Voelkl, who has created scents for Le Labo and Nomenclature as well as Avon and Paris Hilton. "Of course, there are natural ingredients that are extremely expensive, so the use of molecules can be very helpful when you work in a very low-cost range," he says. "But it is also true that some molecules can be extremely expensive. We have woody molecules that cost more than cedar or patchouli oil. The reality is that whether you're working in high-end premium fragrances, niche, or mass market, you're using a combination of both because you need both."

Perhaps the biggest criticism of lab-concocted molecules, however, comes from a suspicion that they are in some way unsafe to inhale or use on the skin—and a general distrust of products with lengthy, multisyllabic ingredient lists. But commercially sold fragrances are now more highly monitored than ever before. Waves of industry regulations implemented in the last few years aligned the U.S. with EU-issued restrictions, resulting in several ingredients being pulled from perfumers' palettes, including both naturals (notably, and controversially, oakmoss, which required the reformulation of such classics as Chanel No. 5) and synthetics. Now new molecules are subject to such rigorous testing for toxicity and biodegradability that it can take years to obtain approval for their use. (Synthetic notes differ from phthalates, chemicals used to give fragrances diffusiveness, which have been shown to have potential endocrine-disrupting effects.)

"Synthetics are simplified molecules," says Carlos Quintero, cofounder of aroma chemical–based fragrance line Nomenclature. "[Perfumers] can purify them until they get a well-tested, nonallergenic molecule. With naturals, there are many more elements that can cause allergies because they are more complex. A synthetic may have five possibilities, but a natural may have 1,000."

"There are 26 potential allergens that we have to list on the back of our boxes, and 18 of them are natural," Matts says. "It's not like one is better than the other. These chemicals go through a lot of testing. We wouldn't be using them if they weren't safe. I think probably one of our biggest problems as an industry is that we haven't educated the consumer about what they really are."

One step in that direction: Perfume brands are beginning to make the case that some synthetics are, in fact, more eco-friendly than naturals. Natural musk, which once had to be extracted—with fatal consequences—from the unfortunate musk deer, is now illegal, as is civet (thankfully, no longer derived from the anal glands of an exotic cat), and endangered crops, such as rosewood, can be protected by using molecular facsimiles. "Synthetic raw materials give us confidence in sustainability—knowing where and how they were made and what exactly is in them," Flores-Roux says. "Your essence of orange or sandalwood may be adulterated or not the best quality. It might not even be the plant it claims to be." "I think sustainability is really important in a discussion of synthetics," Huber says. "It's where the future will be. A lot of naturals come from conflict-ridden areas or are irresponsibly sourced." POP, Stella McCartney's most recent juice, utilized a simulated tuberose note rather than sacrifice the 3,600 flowers it would take to produce a single gram of the natural absolute. The company was also able to claim that for every 2,500 bottles of fragrance produced, one sandalwood tree was saved thanks to the use of a synthetic substitute.

Stella McCartney's most recent juice, utilized a simulated tuberose note rather than sacrifice the 3,600 flowers it would take to produce a single gram of the natural absolute.

After having been, for so long, the unappreciated chorus of perfumery, synthetics are beginning to take the starring role. This began with Escentric Molecules, a brand founded in 2006 by German perfumer Geza Schoen, who realized that many of his favorite fragrances—including Dior's Fahrenheit and Lancôme's Trésor—featured extremely high doses of a cedary, musky molecule called Iso E Super, which is used in some proportion in virtually every commercial scent ("It kind of amalgamates everything together and adds that sparkling woody thing that you can't get with any other ingredient," Quintero says). Schoen decided to try the synthetic on its own, and the result, Escentric Molecules Molecule 01, an eau comprised entirely of Iso E Super, became a runaway hit. He followed this with Molecule 02—the "tobacco-y, amber-y, mineral" Ambroxan—and Molecule 03—the "almost grapefruitlike" vetiveryl acetate.

"I thought Molecule 01 would be for extreme creative types," Schoen says, "but now it's everywhere. Women, men, old people, young people. Someone even keeps sending me pictures of a dog that goes nuts when he smells it."

Nomenclature, the molecule-centric fragrance line launched in 2015, turned the spotlight on four of the twentieth century's groundbreaking aroma chemicals with its first four scents—the white musk Helvetolide; the Hedione-like Paradisone; the woody, Iso E Super–type molecule Orbitone; and iris aldehyde, which first imparted its cool, clean-linen effect to Chanel No. 5. The brand's new offering, Lumen_esce, features Violettyne, what cofounder Karl Bradl calls an "electric violet," which was patented by Firmenich in 2000. "People who usually hate fragrances love these," Bradl says, "because they're very sheer and transparent."

In each Nomenclature eau, the featured molecule is augmented with select naturals, because, Bradl says, "100 percent synthetic fragrances can be a little flat. We're inverting the traditional structure so that the synthetic defines the main character of the fragrance, then naturals are added to round it out." Indeed, Escentric Molecules' success notwithstanding, most perfumers agree that synthetics need naturals, just as naturals need synthetics. "Synthetics give you the modernity and the signature," says Alberto Morillas, the nose behind such blockbusters as CK One and Acqua di Gio. "Naturals give you the beauty." For all the precision and novelty that high-tech molecules can bring, it's the elements that come from living things that provide the poetry, the giddy grip on the heart.

"Naturals confer richness to a perfume," Flores-Roux says. "They're like the gold leaf on the architecture. And personally, I like them for the romance. You can say Cool Water has lots of dihydromyrcenol, but that doesn't really tell a story. Whereas it is fantastic to say in X perfume there is narcissus absolute from the mountains of southern France. It talks to the mystique of the product, and that's something we do in perfumery—we sell dreams."

Original Synths

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1."Iso E Super is one of the most-used ingredients worldwide because it makes every fragrance better, whether it's for floor cleaner, soap, dishwashing liquid, or body lotion," Schoen says. Escentric Molecules' ground-breaking Molecule 01, comprised entirely of Iso E Super, celebrated its tenth anniversary this year.

2.Alberto Morillas blended several different synthetic musks in BULGARI Rose Goldea, the luxury house's sensual new floral fragrance. "When you see a Rothko, you don't see one color, you see many intensities of color," he says. "My signature is to use sensual, floral, woody, and fruity musks in proportion" to conjure a seamless, "voluptuous" effect.

3. To capture the exotic couroupita blossom heart note of Arquiste Ella, Flores-Roux used headspace technology, which, by analyzing molecules in the air, allows perfumers to synthetically reconstruct the scent of a blooming flower without plucking it from the stem.

4. "If we created only with natural ingredients, everyone would be so bored," says Laurent, who tweaked the formula of CARTIER's hit eau to create this nighttime version, La Panthère Édition Soir, adding more intense muskiness and a fresh mimosalike note.

5. For CHANEL No. 5 L'Eau, the new reimagining of Coco's classic, perfumer Olivier Polge enhanced the orange-peel effect of the scent's famously fresh aldehydes. "Each natural oil and each synthetic molecule has a different aesthetic," he says, "like different colors that a painter would use. It's not a matter of quality, it's really a matter of aesthetics."

6. NOMENCLATURE Lumenesce, a "modern violet" created by Voelkl, spotlights Firmenich captive Violettyne, enhancing it with natural notes of jasmin sambac, Bulgarian rose, and bergamot.

7. HERMÈS Galop d'Hermès, a commingling of rose and leather, was built around the warm, spicy Safraleine molecule, which, perfumer Christine Nagel says, "brings femininity beyond the mordant quality of the leather."