Microscopic molecules drift through the air and get trapped on a film of mucus in the back of your nose called the olfactory epithelium. The molecules dissolve and bind to some 40 million special receptor cells, which help fire signals to different regions of the brain. You perceive this as smell. You can trick the brain, though. In a 2001 study published in Perception, psychologist Rachel Herz made people smell the same odors at two different sessions separated by a week. When subjects smelled a mixture of butyric acid (contained in vomit) and isovaleric acid (present in smelly feet), they were told it was “Parmesan cheese.” They responded favorably and said they would like to eat it. But when told it was “vomit,” they wanted to bolt. With those olfactory illusions in mind, try calling your sweaty socks “Parmesan style.”