In biology, axenic (/eɪˈzɛnɪk/, /eɪˈzinɪk/) describes the state of a culture in which only a single species, variety, or strain of organism is present and entirely free of all other contaminating organisms. The earliest axenic cultures were of bacteria or unicellular eukaryotes, but axenic cultures of many multicellular organisms are also possible.[1] Axenic culture is an important tool for the study of symbiotic and parasitic organisms in a controlled environment.