"In vivo" is a Latin term meaning "within the living." It refers to experiments or studies conducted in living organisms, such as animals or humans, to observe biological processes in their natural context. This approach allows researchers to understand how various factors affect living systems, providing insights that may not be possible in artificial environments. In contrast to "in vitro," which means "in glass" and typically involves experiments in controlled laboratory settings, "in vivo" studies can yield more relevant data regarding the effects of treatments, drugs, or interventions. This method is crucial in fields like medicine, pharmacology, and biology for developing new therapies and understanding disease mechanisms.