The illustration shows individual pancreatic beta-cells from a patient with type 2 diabetes and a patient without the disease. Cells were visualized by artificially coloring their fluorescence image according to the deficit in the response of their mitochondria to glucose. Warmer colors show a larger deficit, indicating how much more response is possible when intracellular energy demand is experimentally shut off. Beta-cells from each of the observed type 2 diabetic donors underperformed beta-cells from normal donors in this respect. Interestingly, the maximal possible response in the absence of intracellular energy demand was not impaired, demonstrating that the mitochondrial polarization and downstream insulin secretion is determined by the supply-demand balance of the intracellular energetics in whole.