Elucidation of the components that comprise signaling cascades in cells is a primary theme in molecular endocrinology. These signal transduction pathways are frequently initiated at the plasma membrane by the interaction of a ligand with a cell surface receptor. This interaction can result in activation of a number of pathways that are initiated by stimulation of signaling proteins such as JAK/STAT, small G proteins (such as Ras), or adenylyl cyclase (to generate cAMP). However, when the receptor is coupled to heterotrimeric G proteins such as Gq, phospholipase C is stimulated leading to activation of protein kinase C (PKC) and the generation of inositol tris-phosphate (IP3) which, in turn, releases Ca2+ from intracellular stores (Fig. 1)(1). Alternatively, excitable cells can respond to membrane depolarizing stimuli by altering the gating of voltage-dependent Ca2+ channels. In either case, as depicted in Fig. 1, the increase in intracellular Ca2+ initiates signaling cascades that lead to essential biological processes such as secretion, cell proliferation, differentiation, and movement. Calcium concentrations are only transiently increased, and various signals can result in changes in either the amplitude and/or frequency of such fluxes. The diffusion of calcium in the cell is severely restricted due to the large number of proteins and organelles that can bind to or otherwise sequester calcium. Thus, global intracellular Ca2+ signals result from the coordination and summation of elementary release events that have been called “Ca2+ puffs” and influence the concentration of free Ca2+ in both cytoplasm and nucleus (2).