MRIcro can view medical images such as magnetic resonance imaging (MRI) and computerized tomography (CT/CAT) scans. It can show 2D slices, 3D slices as well as graphs for 4D data (for example, changes over time observed on functional MRI scans). It loads images in the NIfTI format, popular with scientific tools like AFNI, FSL, and SPM. DICOM images can be converted to NIfTI using free tools. The web site includes sample images including photographs of a head from the visible human project. These samples provide an intuitive way to learn about brain anatomy.