Calcium ions (Ca2+) are indispensable for a diversity of signal transduction processes within the human body. They guarantee for instance the unrestricted functionality of the immune system, cardiac function and neuronal signaling. All these processes are governed by a concerted interplay of millions of cells. Within a single cell, Ca2+ mediated signal transduction processes are tightly regulated by a sophisticated interplay of an immense variety of proteins that sense or transport Ca2+. A single defect in one of those proteins can lead to severe dysfunctions such as immune deficiencies, heart problems or neuronal diseases. Thus, a detailed understanding on the function and interplay of the Ca2+ signaling proteins is required to provide potential therapeutic strategies against such diseases.