Hyperinsulinemic hypoglycemia is the commonest cause of persistent and recurrent hypoglycemia in infancy and childhood. It has both transient causes (e.g. infant of diabetic mother, small for gestational age,…) and persistent causes (e.g. K-ATP channel defects, glucokinase mutations, glutamate dehydrogenase mutations…).This essay discusses these causes, shedding light on the most recent diagnostic and therapeutic tools for hyperinsulinism. It also discusses the complications of the disease and the challenges facing pediatricians in management of hyperinsulinism.