INS and type 2 diabetes mellitus: New technologies, including single-cell transcriptomics and mass cytometry, have allowed the field to “drill deeper” into the β-cell mass to more definitively reveal the long-suspected heterogeneity within the insulin+ population (Salomon and Meda, 1986; Pipeleers, 1992; Van Schravendijk et al., 1992), especially across species and in non-diabetic vs. T2D donors (Segerstolpe et al., 2016; Wang et al., 2016a,b; Xin et al., 2016).