Computed micro-tomography (CMT) allows us to visualize 3-dimensional sample image. Such unique capability has contributed to our society, especially in the filed of medical science. In this article, fundamentals of CMT are reviewed in order to encourage further application to other scientific field. Application to high pressure research, developed by the GeoSoilEnviroCARS, the University of Chicago, is given to present an idea about what to do and how to build the system. CMT in transmission electron microscopy is also described in comparison to synchrotron-based tomography.