Elevated intracellular Ca²⁺ concentration plays a very broad role as an intracellular signal, which is formed via Ca²⁺ influx from outside the cell via Ca²⁺ channels in the plasma membrane and via two types of Ca²⁺ release channels (IP₃ receptors and ryanodine receptors) from intracellular stores (ER). Ca²⁺ signaling regulates rapid intracellular responses (contraction, neurotransmitter release, etc.) associated with action potentials in excitatory cells. On the other hand, time-lapse Ca²⁺ imaging of prolonged responses such as immune responses and blood pressure control show repeated rise and fall of Ca²⁺ concentrations (Ca²⁺ oscillations). Such responses are a mechanism to avoid persistent increases in Ca²⁺ concentration and efficiently produce a signal. It may be no exaggeration to say that Ca²⁺ signaling regulates cellular functions in all cell types. This indicates that Ca²⁺ signaling can be used as a starting point to obtain clues for understanding unknown cellular functions. Various physiological functions have been analyzed by applying this approach and visualization techniques, and its application to pharmacology is also expected. In this talk, I would like to introduce these efforts.