Humans are surrounded by tiny living organisms invisible to the naked eye. For the most part, these microorganisms cause no problems; however, when they are pathogenic in nature or are displaced fromtheir natural environment, they can cause infections and disease. This chapter addresses the different life forms of microorganisms and how they may be identified; it also teaches you the proper collection technique for common types of specimens. You will learn about the processes involved in identifying microorganisms, the types of culture media used for these processes, how antimicrobial testing is done, and how quality control fits into ensuring reliable patient results.