By 2014 most of the original screening centres were no longer focussed on probe production. Thus, their generation within the historical MLPCN system ceased. The exercise become controversial in terms of the level of investment put in vs the yield of probes that came out. Nonetheless, a persuasive case for their impact value has been made in terms of the exploration of biological pathways and therapeutic hypotheses as a bridge between biological research and drug development (see 'Advancing Biological Understanding and Therapeutics Discovery with Small-Molecule Probes', 2015, PMID 26046436). However, controversy still lingers because of the challenges of tracking down a consensus full set of structures of that could be well above 300 (see 'Parallel worlds of public and commercial bioactive chemistry data', 2015, PMID 25415348). The total number currently indexed in PubChem is shown in Fig. . While acknowledging the conceptual divergence between probes and drugs, ADEV has much to gain from considering the pragmatic guideline established for the former. Two useful aspects would be first to adopt such guidelines during the later drug discovery stages in vitro.