"For the first half of geological time our ancestors were bacteria. Most creatures still are bacteria, and each one of our trillions of cells is a colony of bacteria"

This quote by Richard Dawkins is a tip of the extraordinary history of life on Earth. It highlights the fact that for the very first half of geological time, the only living organisms were germs. Even today, bacteria are still the most abundant form of life on the planet, and they are important for the performance of the biosphere. Moreover, every one of our trillions of cells is a colony of bacteria, which is a testimony to the importance of germs in our lives. This quote serves as a suggestion of the extraordinary variety of life on Earth, and the importance of germs in the functioning of the biosphere.