“…In principle, we now have advanced tools to measure a large number of phenotypic impacts of a genetic change, for instance through high-throughput microscopy, proteomics, or RNAseq (Manzoni et al, 2018;Ritchie et al, 2015;Zhang and Kuster, 2019). The conceptual problem is how to define phenotypes given the interconnectedness of biological systems (Geiler-Samerotte et al, 2019;Paaby and Rockman, 2013). If a mutation leads to complex changes in cell size and shape, should each change be considered a distinct phenotype?…”