Ask unlimited questions for free
In the United States, there is a birth every 8 seconds, according to the U.S. Census Bureau's Population Clock.
The ratio of hydrogen atoms to oxygen in water (H2O) is 2:1.
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.
Human kidneys will clean about 1 million gallons of blood in an average lifetime.
For a complete list of videos, visit our video library