Our nose is a complicated — and smart — part of or chemosensory system, which consists of the senses of smell and taste. Smell has played an important role throughout human existence in helping us sniff out food, identify predators, communicate socially (such as deciding who’s attractive or trustworthy based on their unique body odor), and navigate the world.

Smell is regarded as one of the most powerful and evocative senses; it can behave as a time machine of sorts in triggering memories, and aids in attraction, love, and sex. Its inner workings are considered more complicated than that of an airplane.

Molecules And Olfactory Receptors

All around us, things like coffee or gasoline emit tiny molecules that can enter our olfactory system in two ways: either through our nostrils or the back of the throat (mostly everything emits molecules, from perfume to bread). We’re mainly familiar with smelling through our nostrils, although eating food which releases molecules into the back of the throat can also cause us to smell.

Once inside your nostrils, these air molecules land on the olfactory epithelium — a tissue covered in mucus that lines the nasal cavity. The epithelium contains millions of olfactory receptors, or neurons that are capable of binding with specific odor molecules. These are the “locks and keys” of the olfactory system, which help identify certain smells. An odor molecule from a cup of coffee floating up into your nose will find and bind to an olfactory receptor that’s specifically designed to identify that molecule. This notion was uncovered by Richard Axel and Linda Buck, who won the 2004 Nobel Prize in Physiology or Medicine for their discovery.

Once the olfactory receptors bind with a specific odor, they send their electrical impulses to a certain microregion, also known as the glomerulus (of which there are some 2,000 in the olfactory bulb), which then passes it along to other parts of the brain. The “odorant patterns” that are released from the glomerulus are interpreted in the brain as smell. 

For a while, it was assumed that the human nose was capable of only smelling 10,000 different scents. It was only recently that scientists overturned that notion with a new theory: that the nose was capable of much, much more, smelling up to one trillion scents. This is because odor molecules have a myriad of different shapes that can fit into several receptors at once, making it possible for the nose to identify more smells than the number of receptors available.

The nose is also considered the “guardian of your lungs,” acting as a filter that retains tiny particles, and humidifies and warms the air you breathe to keep the bronchial tubes moist.

How Smell Impacts Memory

The olfactory bulb, which contains glomeruli, is located in the brain’s limbic system, which is often associated with memory and emotions. The olfactory bulb is also linked to the amygdala, which processes emotion, as well as the hippocampus, known for its role in learning. This is why smell is notorious for triggering memories and powerful emotions — and why you may find yourself transported to a different time when you smell chlorine, the inside of an old textbook, or a long-lost lip balm you used as a pre-teen.

Smell In Social Interaction

Perhaps what is most fascinating about the nose is its role in helping us navigate the social world. On a deeply subconscious level, smelling chemicals, often referred to as pheromones, emitted from another person in their bodily fluids (like sweat and tears) can impact how we view them and even change our own hormones. In past research, pheromones were largely linked to sex and sexual attraction — but new research suggests the notion of “sex pheromones” or “sexy smells” is quite a myth. There are, however, chemicals (pheromones or not) that are emitted from our bodies — even the very subtle smell of tears can reduce sexual arousal and send a signal that mating is not an option during emotional distress, according to a recent study.

While scientists debate over pheromones and whether or not they truly exist, it’s safe to say that our noses — in addition to being the protruding leaders of the rest of our bodies — help us in navigating our social, primal, and nostalgic worlds more so than any other sense.