how we find out about germs by isaac asimovin Hame bacteria or virus ke base me kaise pata chala?

how did we find out about germs

isaac asimov now take us in the world of micro organism .there are lots of questions like what is bacteria?how we came to know that there are single cell organisms?how we know some of them are causes of diseases ?what is vaccination?how we defeat those virus and bacteria ?all those questions are given with interesting history by isaac asimov .