In patients with type I diabetes, tight glucose control prevents long-term complications but increases the risk of hypoglycaemia. In closed-loop systems, subcutaneous glucose monitoring devices are linked by control algorithms to subcutaneous delivery of insulin via a pump. Now (Roman Hovorka and colleagues. Lancet 1020;375:743–51; see also Comment, ibid: 702–3), studies in Cambridge have shown that use of a closed-loop system overnight might reduce the risk of nocturnal hypoglycaemia in children and adolescents with type I diabetes already using an insulin pump. …