Schematic representation of an insulin molecule C254H377N65O76S6, a cross-sected beta-cell (top right in blue) as well as a capillary bed with red blood cells (erythrocytes) and insulin and blood sugar molecules. The beta-cells are found in the islets of Langerhans (islet cells) of the pancreas (hinted in the background). Once secreted from the B-cells (middle window), insulin passes the capillaries to reach muscular tissue (bottom window).