Despite being such a fundamental molecule, the crystal structure of xanthine remains unknown, with crystals too small to be used for SCXRD and complexities arising from strong preferred orientation of crystals affecting powder XRD studies. Recently, the potential for 3D-ED to be applied to purine base compounds has been demonstrated with its use to confirm the SCXRD structure of β-guanine from biogenic samples . In addition, electron diffraction experiments using conventional transmission electron microscopy (TEM) techniques to probe xanthine crystals have predicted a structure similar to that of guanine crystals .