The use of in vitro, in vivo, and in silico approaches can aid the grouping and prioritization of chemicals for testing or assessments by regulatory bodies. This can be done by generating grouping hypotheses and justification for inclusion or exclusion criteria for substances in groups . In particular, novel approaches may generate huge amounts of toxicological and highthroughput "omics" data including metabolomics, transcriptomics, and exposomics to support the validation and establishment of grouping hypotheses needed by regulatory authorities . An example of a grouping hypothesis is the mode of action (MOA) hypothesis, which states that all chemicals that share a common mode of action are candidates for grouping . Additionally, concepts such as adverse outcome pathways and toxicity pathways can be translated into prioritization hypotheses that can target specific substances, hence advancing prioritization for hazard assessment . These can facilitate regulator efforts to restrict hazardous substances.