In 2005 Jennifer Pluznick hypothesised that a gene known to play a role in a common form of kidney disease did so by acting as a master switch for other genes. Lab tests supported her theory; however, when she looked at which genes it acted on, she did a double take. Among them were several that encode scent receptors, the chemical sensors that allow us to identify smells. Pluznick has spent the last eight years trying to understand why. Our noses contain hundreds of different scent receptors that allow us to distinguish between odours. These receptors, as well as similar ones usually found on taste buds, crop up all over our bodies. In 2003, bitter taste receptors were found in sperm. The same year Pluznick came across scent receptors in the kidney, biologists at the University of California, San Diego identified sour receptors in the spine. A smattering of papers over the following few years reported sweet taste receptors in the bladder and the gut, bitter taste receptors in the sinuses, airways, pancreas and brain, and scent receptors in muscle tissue. As these findings became public, researchers poured over genomic data and reported that low levels of these receptors occurred in almost every tissue in the body. Their findings suggest that our bodies are smelling" and "tasting" things deep inside of us, and that these abilities are crucial to our health. What's emerging is a picture of these receptors as a kind of general-purpose chemical sensor. We just happened to come across the receptors in the nose and the mouth first.