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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.
Blood in the urine can be a sign of a kidney stone, glomerulonephritis, or other kidney problems.
Egg cells are about the size of a grain of sand. They are formed inside of a female's ovaries before she is even born.
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.
Certain rare plants containing cyanide include apricot pits and a type of potato called cassava. Fortunately, only chronic or massive ingestion of any of these plants can lead to serious poisoning.