Abstract
Orbital degree of freedom plays very important roles in electric and magnetic properties in strongly correlated electron systems.The method for measurement if orbital ordeing, however, has been limited so far.Recently it has been pointed out that the resonant X-ray scattering (RXS) technique is a very powerful tool to observe the ordering. In this paper, the principle of RXS and the recent development are descrived after the general introduction of orbital degree of freedom.Finally the future in orbital physics will be discussed.
