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Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
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.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
More than 4.4billion prescriptions were dispensed within the United States in 2016.
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