Microbiology is the scientific study of microorganisms, its characteristics and the treatment of the disease producing microorganisms. Microorganisms are the causative agents for all infectious diseases. When the antibiotic was invented scientists thought that the disease producing bacterias will be eradicated from the world. But the organisms started adapting these drugs, it became a challenge to the physicians to treat the infectious diseases. They developed more antibiotics. They grow the microorganisms and tested them with antibiotics to find out which one is more suitable for that particular organism. This test help the physicians to choose the correct antibiotic to treat his patient. Modern days there are many different types of antibiotics and parellely there are many bacterias developed resistance mechanisms. Microbiology is one of the branch of medical science and it is as important as any other disciplines in medical science.