A new study published in the Biophysical Journal applied optogenetics to understand how subpopulations of β-cells control the overall [Ca2+]i response and insulin secretion dynamics of the islets of Langerhans. In this experiment, electrical activity in β-cells of channelrhodopsin-2-expressing islets were spatiotemporally perturbed; the [Ca2+]i response were mapped and correlated with the cellular metabolic activity and an in silico electrophysiology model. The results revealed organized regions of metabolic activity across the islet, which affected the way in which β-cells electrically interact. Additionally, it was found that specific regions acted as pacemakers by initiating calcium wave propagation. The findings of this study disclosed functional architecture of the islet and how distinct subpopulations of cells can disproportionality affect function. Further, it was stated that these results suggest ways in which other neuroendocrine systems can be regulated, and demonstrate how optogenetic tools can discern their functional architecture.