Moving up to PubChem provides not only another scale jump in compounds but also a concomitant expansion in relationship statistics (see 'PubChem 2019 update: improved access to chemical data', 2019, PMID 30371825 and Fig. ). This complexity (but also the navigational power) is magnified because of the embedding of PubChem within the NCBI Entrez network of ~ 20 interconnected databases (see 'Database resources of the National Center for Biotechnology Information', 2019, PMID 30395293). Notwithstanding the engagement challenges, there are many reasons why it is a must-stop-shop for ADEV, only a few of which can be pointed out here. Note also that PubChem and Entrez are cases where collaboration with specialists familiar with their broad sweep of features is necessary for maximal exploitation. While UniChem (see PMID 29451740) is ~ 160 million (but cannot be similarity searched) and vendor virtual collections are now pushing towards the billions, PubChem remains the largest public source of just short of 100 million chemical structures that are (at least mostly) extant (see 'PubChem Sources by the numbers, 2016, blogpost).