Ask unlimited questions for free
There are 20 feet of blood vessels in each square inch of human skin.
A seasonal flu vaccine is the best way to reduce the chances you will get seasonal influenza and spread it to others.
There are more nerve cells in one human brain than there are stars in the Milky Way.
The first documented use of surgical anesthesia in the United States was in Connecticut in 1844.
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.
For a complete list of videos, visit our video library