The experts say this is the beginning of the golden age of microbiology. Industry, medicine, the definition of life itself, are all being changed by single-celled creatures you and I can't even see. But the news is not all good. Many people are spooked by the diseases caused by bacteria: Pneumonia, Salmonella, meningitis... all caused by bacteria and passed among us every day. Infectious diseases are the greatest cause of illness and death in human history. Bacteria can make us deathly sick and often kill us. And just when we develop medicines to kill the germs, they do what they do best... mutate, find ways to resist our medicines. Now we are bombarded with products that promise to kill these germs. The number of new antibacterial products has tripled. But does the use of these products just make the germs even more resistant? At the same time, the search for new microbial life has taken researchers from the lab to the ocean floor and to the heavens. A meteorite from Mars has fossilized structures on it that look suspiciously like small bacteria. Scientists are coming to the conclusion that life may be far more common in the universe than we had supposed. Anywhere that there is liquid water, there is a possibility of life, and, in fact, anywhere on Earth where there is liquid water, you find there is life. And so on worlds such as Mars or Europa where there may be hydrothermal features under the ice, the prospect of finding microbial life is very exciting.