In vivo testing refers to the process of conducting experiments or studies on living organisms to evaluate the effects of a certain treatment, drug, or intervention. This type of testing is typically used in biomedical research to better understand the biological mechanisms of a disease or to test the safety and efficacy of new therapies. In vivo testing can involve a wide range of organisms, including mammals, rodents, fish, insects, and bacteria. This type of testing is often conducted in controlled laboratory settings to ensure that the results are reliable and reproducible. In vivo testing is an essential step in the drug development process and is used to determine the potential benefits and risks of a new treatment before it is tested in clinical trials involving human subjects.