The microbiologist is a biologist specializing in microbes, scientifically called microorganisms: viruses, yeasts, molds and microscopic fungi, bacteria, microscopic algae, etc. These are present in all environments: soil, air, water, inside our body, etc. His job is to carry out analyzes and experiments in the laboratory, using instruments precision, like a microscope. He uses techniques such as isolation: he is able to isolate, characterize and identify a particular microorganism. In Petri dishes , he develops culture media for bacteria, yeasts, etc. By changing the composition of the environment, he can transform their activities, regulate their growth, and even modify certain details of their genetic structure without causing their destruction. After having developed theories and depending on the results of experiments carried out, he or she validates them or not.