Microorganism affect the well-being of people in a great many ways and occur in large numbers in most natural environments. They may be tiny, but the relative new science of microbiology is huge! Prokaryotic bacteria, eukaryotic fungi, and nonliving viruses are just some of the microbes that have much effect on our health and environment. The field of microbiology can be generally divided into several subdisciplines, such as microbial physiology, microbial genetics, cellular microbiology, veterinary microbiology, environmental microbiology, evolutionary microbiology, industrial microbiology, food microbiology, agricultural microbiology, medical microbiology, pharmaceutical microbiology, etc.