Although magnesium ion (Mg(2+)) is believed as an important factor for maintenance of normal neuron function, our understanding of its intracellular mobilization and physiological function is still not enough. We need to know the following mobilization mechanisms of Mg(2+) in neurons:Mg(2+) influx via ion channels, Mg(2+) release from intracellular pools, and Mg(2+) transporters located on cell membrane. In this short review, I show the recent findings of intracellular Mg(2+) release and also Na/Mg antiport on cell membrane in PC12 cells that have been revealed by fluorescent Mg imaging techniques.