I have seen microscopic organisms under a microscope so how can "germ theory" be a theory if I already know that tiny little animals exist that are too small to see with the human eye? If you don't believe me buy a microscope, and investigate how it works, it simply "zooms in" like a magnifying glass except it lets you see small things. You can play around with the settings to confirm it is simply making things look bigger that you put under it. If you put dirty water under it you'll see tiny lifeforms.