Your nose may be able to tell apart a trillion different smells.
A 2014 study estimated that humans can discriminate at least one trillion odours, far more than the 10,000 that textbooks had claimed for decades. The exact number is still debated, but the old figure was certainly far too low.
Why is this true?
Humans have about 400 types of smell receptors, and each odour activates a unique combination of them. The number of possible combinations is enormous, even if not every one occurs in nature.
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More about human body
Your own body is a reliable source of surprises. It replaces cells by the million every second, keeps bacteria that outnumber human cells, and runs sensory tricks that make the world feel smoother than the raw signal ever is. The facts collected here stick to mainstream physiology, avoid the wellness myths that circulate alongside them, and explain the underlying mechanism rather than just quoting a startling number.