What happens when you take a reassuring whiff of your morning coffee or recoil in horror when you sniff the cream and realize it’s gone bad?
Your nose is loaded with special cells called "olfactory sensory neurons," and each of these neurons has one (and only one) odor receptor. When many molecules in the air around you stimulates one of these odor receptors, it sends a message directly to the brain, explains Justin Turner, otolaryngologist and director of the Smell and Taste Center at Vanderbilt University.
