In biomedical research, there are two main types of experimental models used to study human diseases: in vitro models and in vivo models.

In vitro models are experiments conducted in a laboratory setting using isolated cells, tissues, or organs. These models provide a simplified and controlled environment in which to study disease mechanisms and test potential therapies. Examples of in vitro models include cell cultures, organoids, and tissue slices.

In vivo models, on the other hand, are experiments conducted in living organisms, such as animals or human subjects. These models provide a more complex and dynamic environment in which to study disease processes, but are also subject to more variables and ethical considerations. Examples of in vivo models include mouse models of cancer, humanized mouse models, and clinical trials in human subjects.

Both in vitro and in vivo models have their advantages and limitations. In vitro models are useful for studying the basic biology of diseases and for screening potential drug candidates, but they lack the complexity of the whole organism and may not accurately represent the disease in vivo. In vivo models are more complex and can better represent the disease in its natural environment, but they are subject to ethical considerations and may not always accurately predict human disease outcomes.

Thus, researchers use both in vitro and in vivo models to gain a comprehensive understanding of disease mechanisms and test potential therapies before moving to clinical trials.