We report the first experimental soft-tissue phase-contrast tomography results using a conventional x-ray tube source, with a millimeter-sized focal spot. The setup is based on a Talbot-Lau grating interferometer operated at a mean energy of 28 keV. We present three-dimensional ex vivo images of a chicken heart sample, fixated in formalin. The results clearly demonstrate the advantageous contrast attainable through phase-contrast imaging over conventional attenuation-based approaches.