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The human body produces and destroys 15 million blood cells every second.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
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.
This year, an estimated 1.4 million Americans will have a new or recurrent heart attack.
There used to be a metric calendar, as well as metric clocks. The metric calendar, or "French Republican Calendar" divided the year into 12 months, but each month was divided into three 10-day weeks. Each day had 10 decimal hours. Each hour had 100 decimal minutes. Due to lack of popularity, the metric clocks and calendars were ended in 1795, three years after they had been first marketed.