Calcium cations (Ca 2+) play an important role in the cellular signaling and in a number of physiological processes. The cell Ca 2+ distribution is exactly regulated by transport systems which maintain low free cytosolic calcium concentration ([Ca 2+ ] i) (50-100 nmol/l) in comparison with Ca 2+ concentration in extracellular space (about 1.3 mmol/l). The plasma membrane possesses several types of channels which control the Ca 2+ entry into the cells, and systems that extrude it. Calcium enters the cell by any of the general classes of channels, including voltage-operated channels (VOC), second messengeroperated channels (SMOC), store-operated channels (SOC) and receptor operated-channels (ROC). Calcium release from the cells is regelated principally by Ca 2+-ATPase, and Na + exchanger (Figure 1). Plasma membrane is responsible for the 10,000-fold gradient of Ca 2+ normally measured between the extracellular space and the cytoplasm. The very large gradient of Ca 2+ across the plasma membrane not only ensures full availability of the cation, but it is also dynamically beneficial, since even minor changes in the Ca 2+ permeability of the plasma membrane provides significant fluctuations in the [Ca2 + ]i. Passing Ca 2+ through the plasma membrane triggers a cascade of events that are vital for cellular activities. Calcium cation is an important ubiquitous messenger, controlling a broad range of cellular processes. It has a direct role in controlling the expression patterns of its signaling systems that are constantly being remodelled in both, health and disease.