Ask unlimited questions for free
About 600,000 particles of skin are shed every hour by each human. If you live to age 70 years, you have shed 105 pounds of dead skin.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
About 3% of all pregnant women will give birth to twins, which is an increase in rate of nearly 60% since the early 1980s.
Vaccines prevent between 2.5 and 4 million deaths every year.
The human body produces and destroys 15 million blood cells every second.
For a complete list of videos, visit our video library