In vitro

In vitro (literally 'in glass') describes an experiment done in a controlled or artificial environment such as a test tube. It serves as a reminder that the result of the experiment will not necessarily be the same in other environments. In biology, in vitro generally means outside the body, so when a drug candidate is shown to be effective in vitro, this might mean that it kills isolated cancer cells in culture, but may not be effective at fighting cancer in a whole person (in vivo).