a simple organism belonging to a prokaryotic system consisting of a single cell.Germs are one of the smallest germs, most of which are about 0.3 to 2 micrometers in diameter. You can only see through a microscope. Germs exist everywhere in humans, thousands of species, and most of them are harmless to humans.Some germs live in the intestines of humans and animals and help digest food and destroy harmful creatures. And they also make the vitamins that the body needs.Bacteria that live in soil and water play an important role in the circulation of various chemical elements, including carbon, nitrogen and sulfur, which are necessary for living things. Germs decompose the excrement of dead organisms and animals into chemical elements.If not broken down by bacteria excrement or dead organism constitutes the chemical elements are preserved to all living things is no longer will not live.Germs also convert chemical elements into forms that can be used by plants and animals. For example, some bacteria turn nitrogen in the air or soil into nitrogen compounds that are available to plants. Fermentation used to make alcoholic beverages, cheese, and many other foods is caused by many kinds of bacteria.It is also used to cleanse water or make medicine at a sewage treatment plant.Bacterial cells are similar in many ways to those of other living things.So scientists learn about more complex creatures by studying germs.For example, scientists are using germs to find out how certain traits are inherited.Germs are fast breeding, so they can quickly grow the amount needed for research.