X‐ray microscopy microscope installed at the beam line ID21 at European Synchrotron Radiation Facility (ESRF) was used for the elucidation of micro‐distribution of vanadium in ascidians. In order to examine chemical states of vanadium in the alive blood cell, a high pressure cryo‐fixation technique was applied to fix its chemical states of vanadium. We have succeeded in observing uniform distribution of vanadium in the vacuole, in identifying the valency of vanadium in the cell, and more importantly in finding granules rich in vanadium of the 4th valency. © 2004 American Institute of Physics