Our bodies are pretty amazing. Day after day, they work hard — digesting food, pumping blood and oxygen, sending signals from our brains and much more.

But there is a group of tiny invaders that can make our bodies sick — they're called germs.

Some kids may think that germs are bugs or cooties or other gross stuff. Actually, germs are tiny organisms, or living things, that can cause disease. Germs are so small and sneaky that they creep into our bodies without being noticed. In fact, germs are so tiny that you need to use a microscope to see them. When they get in our bodies, we don't know what hit us until we have symptoms that say we've been attacked!