Definition: In vivo
comes from the Latin term "in life" and refers to studies of biological properties that are performed inside a living organism. As opposed to in vitro
("in glass") studies which are done inside a test tube, in vivo
studies allow scientists to look at scientific and medical questions within the context of a living organism. Unfortunately, this makes them far more expensive, and often more difficult, than in vitro
studies. However, there are some questions that can only be fully addressed by looking at them in the context of a living organism.