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Human neurons are so small that they require a microscope in order to be seen. However, some neurons can be up to 3 feet long, such as those that extend from the spinal cord to the toes.
According to the FDA, adverse drug events harmed or killed approximately 1,200,000 people in the United States in the year 2015.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
Illicit drug use costs the United States approximately $181 billion every year.
Hippocrates noted that blood separates into four differently colored liquids when removed from the body and examined: a pure red liquid mixed with white liquid material with a yellow-colored froth at the top and a black substance that settles underneath; he named these the four humors (for blood, phlegm, yellow bile, and black bile).