Samples from commercially acquired xanthine (see S1) were deposited onto TEM grids. 3D-ED datasets from multiple sub-micron sized crystals of xanthine were collected and processed, with each comprising of a tilt series of diffraction patterns (as described in Methods). In some datasets from a single particle (Figure ), the presence of two separate reciprocal space lattices were observed upon the reconstruction of the 3D reciprocal space (Figure .1). The low overlap of reflections enabled successful integration and structure solution treating the reflections from each reciprocal lattice as independent, thus splitting the data set into two. Each data set was consistent with Form I xanthine .