We are living in the age of malodor amelioration. You smell better now-and will smell even better in the future-because of the advances that are occurring along Interstate 95 between Philadelphia and Newark. You could call that stretch of road “the stink highway.” This revolution began in 1990, when George Preti, a scientist at the Monell Chemical Senses Center, in Philadelphia, isolated the specific molecule (3-methyl-2-hexenoic acid) that produces the distinct odor of underarm sweat. Before Preti’s discovery, you had to, in his words, “carpet bomb” smells by applying a perfume strong enough to overwhelm and erase all odors. Once Preti cracked the code, scientists could create scents that adhere only to the nasal sensors that are most sensitive to 3-methyl-2-hexenoic acid. Deodorant designers are now able to create precisely the scent they want, which could be no discernible scent at all. Along the stink highway, all the stages of innovation are on display. Sixty miles northeast of Preti’s lab, I visited the International Flavors & Fragrances research-and-development center, in Dayton, New Jersey. Michael Popplewell, a scent scientist there, takes basic research, like Preti’s, and transforms it into chemicals that consumer-products companies can buy. His team works on masking odors from bathrooms, garbage cans, and baby diapers. (Researchers at other companies specialize in agricultural stenches, like manure.) Popplewell says that the cutting edge of research is in stopping bad smells before they start. One promising idea is to use probiotics to replace the microorganisms that cause bad odors with ones that cause more benign smells.Ten miles up the road from I.F.F. is the factory that produces Power Stick, a low-cost deodorant sold in bargain stores like Dollar General and Family Dollar. Fred Horowitz, the C.E.O., showed me around the plant, where dozens of workers combine ingredients-silicon, scent, aluminum sesquichlorohydrate-and operate a machine that squirts the mixture into plastic containers. I wondered why this plant, where a cheap, lightweight commodity is produced by workers who require no advanced education, was in the U.S.; this is the kind of manufacturing more often done in China or Mexico. If retailers are selling Power Stick for a dollar, Horowitz can’t be making much more than a penny or so per stick. I asked if he thought he could increase profits by moving to a country where wages are lower. “No,” he answered. “I’m in the center of all the innovation. It’s all happening here in New Jersey.” Major scent companies, as well as logistics managers, branding consultants, and firms developing new packaging and production techniques, pitch their innovations to Horowitz and the many other cosmetic manufacturers nearby. This constant interaction led Horowitz to adopt a technique called microencapsulation, a deodorant breakthrough in which microscopic balloons filled with scent melt at specific temperatures or after a certain amount of time. By staying in New Jersey, Horowitz has access to this fast-moving consumer-goods network. It’s an advantage that outweighs, at least for now, the savings he would achieve by moving to a different country. Michael Porter, a professor at Harvard Business School, applied the term “cluster” to phenomena like the stink highway: agglomerations of businesses that find it profitable to stay close to one another. There are famous industry clusters, such as Hollywood, Silicon Valley, and Wall Street. But there are many others. Warsaw, Indiana, has a cluster focussed on orthopedic devices; Wichita, Kansas, is big on aircraft.Clusters can be delicate things that grow slowly, even accidentally, over decades. If Dave Packard and Bill Hewlett hadn’t become friends at Stanford, in 1934, Silicon Valley would likely not exist some eighty years later.