It is impossible to see Micro-Organisms with the naked eye unless a large amount of them group together, which is called a colony. Micro-Organisms  can live anywhere, from under water to dry deserts. While some Micro-Organisms can cause diseases, some can cure them. Such as Penicillin, Penicillium can cure diseases  caused by bacterial growth. Penicillin is the drug and Penicillinis the mould.  Dr Fleming  discovered  that the bacteria that he was studying was interffered by a Micro-Oganism called Penicillum.