Second, non-invasive imaging techniques are also important for marmoset research. Conventional histological techniques, such as sectioning of tissues, require the destruction of specimens of sacrificed animals. As a result, it is impossible to monitor anatomical changes of the same animal over long periods by conventional methods. In addition, for primate research, the number of animals available for research is another issue, because of cost and ethical issues. Magnetic resonance imaging (MRI) is a non-invasive imaging technique to visualize internal structures of the body in detail, and is used for medical diagnosis.