Disclaimer: This visuals in this clip may be discomforting. In this visualization of 18th century medicine, Abigail Adams and her children get inoculated against small pox. Innoculation was pioneered in the West by Edward Jenner.

What is cancer, and how does it start? Find out how genetics play a role, which types of cancer are the most prevalent, and what is being done to fight this deadly disease.

This clip shows the different biosafety levels of a research facility. For each level, it lists the types of microorganisms that exist along with some of the viruses they could cause. It also shows the equipment and safety precautions used by the researchers at each level.

The Eds are trying to sell ice cream to the other kids in the cul-de-sac, but no one appears to be around. They ring Jimmy's doorbell to see if he is home, and they are surprised to see that he has chicken pox. The Eds notice quarantine signs in front of everyone's house, meaning that they are the only ones who did not fall victim to the disease.

A parent grapples with her son's unrelenting fever and talks to the doctors about the possible diagnosis. After finding out that the Strep result was inaccurate, the doctors determine that the patient has Kawasaki disease and put him on the treatment.