The human eye can distinguish roughly ten million different colours.
Colour vision comes from just three types of cone cells, sensitive to red, green and blue light. The brain compares their signals to produce the millions of shades we can tell apart.
Why is this true?
A small number of people, mostly women, carry a fourth type of cone and may see even more. Many birds and insects also see ultraviolet, which is invisible to us.
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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.