1. Olfactory bulb:
As the middleman between your nose and your brain, it transfers smell information to help you distinguish key odors from other smells that occur at the same time. It's an indispensable part of our survival instinct as humans, helping us find edible food and allowing us to distinguish between friend and foe.
2. Olfactory receptor neuron (ORN):
In our nasal cavity about 40 million olfactory neuron receptors are waiting to catch different odors to send them on to the olfactory bulb. Individual ORNs have a cycle of about 40 days. So there is a constant turnover of new cells occurring in the nasal passage.
3. Nasal cavity:
A large part of it has absolutely nothing to do with smell. Its primary function is to purify the air we breathe before it reaches our lungs. The moisture in the nasal cavity dissolves odor particles into liquid form so that the olfactory neurons can detect them.
4. The limbic system:
Long before we can speak, we develop this set of structures as children. It's an emotional memory bank, storing all our happiness, sorrow, fear, pleasure and anger—assigning feelings to different stimuli. And since scent can tap straight into the limbic system, it can evoke emotions from our past without our permission.