This is the story of how Louis Pasteur expanded on the understanding of microbes - more specifically, how bacteria grow via biogenesis versus the previously held belief in spontaneous generation. This book outlines the way in which Pasteur came to this field of study and how he conducted his experiments to reach his conclusion. Finally, the afterword describes his continuing work in the field and his eventual development of the process we now call pasteurization.
Even though this is a very simple examination of the subject, this could still be a rather heavy read for some young children. We broke it up over the course of a few days to make it a bit more digestible. This is a solid book for a unit study on germs, but perhaps not the best pick for a leisurely read unless a kid is really into microbiology...which I'm sure is super common ;-)