Mmm-mmm, microbes! Although we are accustomed to equating the presence of microbes with disease, in fact most microbes play a vital "friendly" role in shaping our lives. It is not just that one hundred million microbes can populate a thimbleful of fertile soil, or that many millions live happily in as much of our saliva. Microbes are everywhere, and we could not survive without them. To emphasize their amazing ubiquity, Jeanette Farrell considers...