We have studied the physical structure, optical property, electronic band structure and atomic structure of europium oxide (EuO) nanocrystals. The physical structures of nanocrystals are confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The optical property and electronic band structure are studied by X-ray absorption near-edge structure (XANES) measurement. We have also investigated the L-3-edge energy of europium(II) ion by extended X-ray absorption fine structure (EXAFS) measurement, which clarified the atomic structure of europium oxide nanocrystals. (C) 2008 Elsevier B.V. All rights reserved.