Closed-loop automated insulin delivery system. The continuous glucose monitor (CGM), depicted as the black rectangle, measures interstitial glucose concentrations every 5-10 minutes, and transmits these data to a controller (red handheld device) wirelessly. The controller houses an algorithm engineered to modulate insulin pump delivery (blue device in pocket) based on CGM data. This alters the glucose with the aim of maintaining a set target. The cycle is repeated, hence the term “closed-loop”. Adapted from Hovorka R. Closed-loop insulin delivery: from bench to clinical practice. Nature Reviews Endocrinology, Springer Nature. 2011; 7(7):385-395 (10) reprinted with permission and Bally, L. et al Closed-loop for type 1 diabetes—an introduction and appraisal for the generalist. BMC Med 15, 14 (2017) (11): Open Access CC-BY 4.0. http://creativecommons.org/licenses/by/4.0/.