The influenza virus is an recurring nightmare, killing thousands of people each year. Learn how the virus attacks its host, why it's nearly impossible to eradicate, and what scientists are doing to combat it.

What is plague? How many people died from the Black Death and the other plague pandemics? Learn about the bacterium behind the plague disease, how factors like trade and urbanization caused it to spread to every continent except Antarctica, and how three devastating pandemics helped shape modern medicine.

The host explains how a virus is like the coronavirus mutate from person to person. They also provide an in-depth and explanation of what makes these mutations dangerous or not depending on their circumstances.

Beakman explains that shoes stink because of the bacteria on your feet. He uses a microscope to quickly show that there are bacteria everywhere and then a short animated clip to show how your feet produce oil and sweat that the bacteria eat. This creates smelly biproducts to make your feet stink. He then does a DIY bacteria growth experiment where he grows bacteria from his sweaty feet in a jar of gelatin.

Hank shows us how humans classify groups of biological organisms based on their similar characteristics.