The conversion of glucose to glycogen is activated and controlled by insulin. Conversion of glucose to glycogen is called glycogenesis.
Glycogen is the principal form in which glucose is stored. The storage is done in the liver and also in muscle cells.
Glycogenesis is stimulated by the hormone insulin and takes place when blood sugar levels are sufficiently high to allow excess glucose to be stored in the liver and muscle cells.
Insulin facilitates the uptake of glucose into muscle cells though it is not required for the transport of glucose into liver cells. However insulin has a profound effect on glucose metabolism in liver cells stimulating glycogenesis and inhibiting glycogenolysis, the breakdown of glycogen to glucose.