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 NIfTI, NRRD, Philips PAR, Bio-Rad Pic, ITK MetaImage, AFNI BRIK, Freesurfer MGH, and DICOM formats (for images saved as 2D slices, you may want to first convert them to 3D volumes using a free tool like dcm2nii). 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.