While the conventional wisdom states that the interior problem - to reconstruct a region of interest (ROI) only from projection data through the ROI - does not have a unique solution, in June 2007 we published the first paper on interior tomography to solve the interior problem exactly and stably, aided by the prior knowledge on a subregion in the ROI. We underline that interior tomography is potentially a powerful, even indispensable tool to handle large objects, reduce radiation dose, suppress scattering artifacts, refine image quality, decrease engineering cost, increase system functionalities, and boost scanner throughput in many biomedical and other applications. Interior tomography can be extended to other similar tomography modalities including MRI, ultrasound tomography, SPECT and PET.