Xanthine (3,7-dihydropurine-2,6-dione) belongs to the purine family and is made of five-and six-membered heterocyclic rings: this chemical skeleton is also found in other purines, such as guanine. It serves as an intermediate in nucleic acid metabolism, acting as a precursor for the synthesis of uric acid and is therefore widely found in organisms and of interest in a pharmacological context . In previous work , 3D-ED was used to elucidate the structure of xanthine (Form I). The Form I xanthine structure consists of hydrogen-bonded layers with weak inter-layer van der Waals' forces (Figure ). However, X-ray powder diffraction (XRPD) of the bulk sample shows asymmetric peak profiles and the presence of peaks which do not match the Form I unit cell, indicating the presence of both planar disorder and other phases respectively . As a fundamental organic molecule with a layered structure, xanthine serves as an exemplar system to study the structural behaviour of this class of layered organic molecular crystals.