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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 Gabriel Fahrenheit invented the first mercury thermometer, he called "zero degrees" the lowest temperature he was able to attain with a mixture of ice and salt. For the upper point of his scale, he used 96°, which he measured as normal human body temperature (we know it to be 98.6° today because of more accurate thermometers).
The familiar sounds of your heart are made by the heart's valves as they open and close.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
It is widely believed that giving a daily oral dose of aspirin to heart attack patients improves their chances of survival because the aspirin blocks the formation of new blood clots.