Japanese company TDK has recently developed a 320GB optical storage disc. In contrast to usual DVDs and BDs, the 320GB TDK disc seems to operate because of difference in reflectivity between two glassy phases within the recording layer. It is suggested that irradiation using a 405 nm laser transforms the non-stoichiometric BiOx (2.5 < x < 3) composition into stoichiometric Bi2O3 glass with ¿dissociation¿ of excessive oxygen. This process causes the large optical contrast. We¿ve just carried out first HE-XRD measurements which show the amorphous nature of the original BiO3 and final Bi2O3 glasses. However, insufficient x-ray sensitivity to oxygen in the presence of bismuth seriously restricts the understanding and reliable interpretation of the structure and laser-induced processes. We propose to use advanced neutron diffraction at ISIS to understand a new way of optical recording.