Micro-Evolution, Compatibility-Evolution and Mutation-Evolution, i.e., bacterium, bacillus, virus i.e. too small to be seen by light microscopy. Harmful bacteria is associated with diseases, epidemics, pandemics, plagues etc., as well as things like; bad odours, skin irritations etc., to abscesses, and infections of a wide range - but it's also found elsewhere in other things too e.g. food bacteria's; cheese/yogurt, bread, beer. There is also the so-called 'friendly bacteria' branches, if you wish to word it that way - essential bacteria, useful bacteria etc., inside the body and outside. And all this doesn't just revolve around human beings either, this level of evolution affects pretty well all living things, as well as equally of dead things, and even what we might consider the inanimate things too such as rocks etc., in the soil, in the water etc., etc. But not everywhere unconditionally no, though this form of evolution can been found in the ultra-extreme environments which Earth humans until recently thought no life could possibly exist, such as on stars/suns and it's found in space etc., deep-ocean, and extremely radioactive environments etc. but of course in those environments everything is proportioned; it doesn't necessarily mean it could survive if taken out of that environment. And there are places which are entirely sterile of any form of life whatsoever too, but there is usually a considerable reason for that - there's a reason for everything.
It's a form of life which exists in many cases beyond the consciousness of the human, animal, higher animal etc., this is how it is successful in many cases as a form of life. It is possible to eradicate/kill just this level of life with a very finely calibrated scientific frequency/sound wave/fine-material wave etc., of some form or another. Which can be used to say cure a person of very many different ailments, problems they are facing from this level of life with a small hand-held device - the Plejaren revealed in a contact report conversation.