1. Microbes

2. So how small are microbes? Well, let's say we could enlarge an average virus, the smallest of all microbes, to the size of a baseball.

3. An average bacterium would then be the size of the pitcher's mound.

4. And just one of the millions of cells that make up your body would be the size of the ballpark!

5. © David Phillips/Visuals Unlimited Microbes have been around longer than ANYthing else on earth—longer than dinosaurs, plants or people. Here's the clue to prove it: fossils of single-celled creatures that date back at least 3.5 BILLION years! We humans only came on the scene about 2 million years ago. 3.5 billion-year-old microbes

6. If you imagine all time since the Earth began as a single day......microbes would have appeared sometime around 5:00 a.m....

7. ...dinosaur s don't pop up until around 10:00 at night...

8. ...and we humans don't figure in until just seconds before midnight!

9. Courtesy of NASA Some scientists even believe there is the possibility bacteria may have once lived on Mars. This photograph taken through a microscope shows what some scientists believe may be the fossils of tiny bacteria in a rock that formed on Mars about 4.5 billion years ago. The rock crash-landed on Earth as a meteorite thousands of years ago.