In addition to advancing our understanding of planar molecular crystals, this area of study could also have wider implications in the pharmaceutical industry, where there is a regulatory requirement to understand and characterize polymorphic forms . This is a topic of interest, where pure polytypes exist, given the range of properties that different polymorphic crystal forms may have . Given that ED has shown a range of crystalline order is possible within individual particles of xanthine, further thought is needed on the way that the solid-state landscapes of layered compounds more generally are described: the interchangeability between different polytypes at the nanoscale introduces an inherent complexity to defining and grouping discrete polymorphs.