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Blood in the urine can be a sign of a kidney stone, glomerulonephritis, or other kidney problems.
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.
There are more nerve cells in one human brain than there are stars in the Milky Way.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
About 3.2 billion people, nearly half the world population, are at risk for malaria. In 2015, there are about 214 million malaria cases and an estimated 438,000 malaria deaths.