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There are more nerve cells in one human brain than there are stars in the Milky Way.
Your skin wrinkles if you stay in the bathtub a long time because the outermost layer of skin (which consists of dead keratin) swells when it absorbs water. It is tightly attached to the skin below it, so it compensates for the increased area by wrinkling. This happens to the hands and feet because they have the thickest layer of dead keratin cells.
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.
There are more bacteria in your mouth than there are people in the world.
HIV testing reach is still limited. An estimated 40% of people with HIV (more than 14 million) remain undiagnosed and do not know their infection status.