The second is that, as the human proteome coverage of probes expands, they provide more potential starting points for drug discovery and subsequent ADEV. Indeed, a publication on the large-scale prediction of probe-like molecules from ChEMBL indicated the chemical tools (most of which could not stringently be classified as probes) were available against 2,220 human targets ('Objective, Quantitative, Data-Driven Assessment of Chemical Probes . This publication includes a useful set of icons to illustrate the scores associated with chemical probe criteria (Fig ). Combinations of these sets can be merged and mapped into PubChem but it is important to note that Probes & Drugs does not submit to PubChem which would add confounding circularity. The extent of confusion around probe structures has been compounded by the merging of both the Advisory Board-scored compounds and historical non-probes (i.e. previously designated as probes but subsequently considered to be inferior and potentially misleading) in the set of 466 CIDs submitted to PubChem by the Chemical Probes Portal.