A healthy (non-colorblind) human eye can distinguish between 500 shades of gray.

A healthy (non-colorblind) human eye can distinguish between 500 shades

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There is enough iron in your body to make a nail 8cm long!

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A single human hair can support up to 3kg

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The retinas inside the eye cover about 650 square mm and contain 137

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Men’s hair is about twice as thick as women’s

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The shark cornea is nearly identical to the human cornea, and has even

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When you blink, it lasts for about one tenth of a second