The human nose can distinguish thousands of different smells, though estimates vary quite widely.

The longer version

Olfactory receptors in the upper part of the nasal cavity sit on nerve cells that project directly into the brain. Humans have several hundred receptor types, and each one responds to a range of molecular shapes rather than a single scent.

A real smell activates a particular combination of them, and the brain reads that pattern, which is how a limited set of receptors can distinguish a very large number of odours. Signals also travel to regions involved in memory and emotion, which explains why a scent can bring back a place instantly. Sensitivity differs widely between individuals and fades with age.

Where this entry sits

These facts look at how the human body works in ordinary moments, from breathing and blinking to balance and sleep. They focus on anatomy, senses, and small reactions that happen constantly without any conscious effort. The full list sits on the Human Body page, where every entry is listed in order.