To one person, a beet might smell mildly earthy and pleasant. To another, sharp and intense. The beet is the same, the earthy odorant—2-ethylfenchol—is the same, but the perception of that odor is different. Researchers have long wondered how that can be, and a team of scientists thinks that perception is linked to tiny genetic changes that alter the activity of some of the hundreds of odor receptors in the human nose. The research, led by Casey Trimmer, an odor scientist formerly of Monell Chemical Senses Center, involved asking more than 300 volunteers to smell a panel of 68 substances and rate the smells according to parameters such as pleasantness and intensity. Then the team took blood samples from the volunteers and sequenced genes for 400 known odor receptors from each volunteer. The researchers found that subtle mutations in single receptors affected how well the receptor worked, and those changes matched how the volunteer perceived the receptor’s target odorant. For example, mutations in OR11A1, the receptor that interacts with the beet odorant, matched the volunteers’ perceptions that beets smell intense or pleasant, Trimmer says (Proc. Natl. Acad. Sci. U.S.A.2019, DOI: 10.1073/pnas.1804106115). She adds that this research shows that while odorants like 2-ethylfenchol or guaiacol, the smoky flavor found in some foods and spirits, might interact with several odor receptors, it’s their actions on individual receptors that seem to lead to perceptions of pleasantness or unpleasantness. “Our sense of smell may be more unique than we thought,” she says.