Ask unlimited questions for free
Asthma occurs in one in 11 children and in one in 12 adults. African Americans and Latinos have a higher risk for developing asthma than other groups.
Vaccines prevent between 2.5 and 4 million deaths every year.
The B-complex vitamins and vitamin C are not stored in the body and must be replaced each day.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
For a complete list of videos, visit our video library