The usage of calcium ions to drive intracellular processes and for communication is called calcium signaling. It is generally a step in signal transduction. Calcium can also function as second messengers wherein they fulfill tasks such as neuronal transmission, cellular motility, muscle contraction and cell growth. Within neurons, concomitant rise in mitochondrial and cytosolic calcium ions are integral to the synchronization of mitochondrial energy metabolism and neuronal electrical activity. However, high level of cytoplasmic calcium ion can cause the cell apostosis. The influx of calcium ions also triggers the development of the oocyte in numerous species. In the case of fish and echinoderms, this influx takes place as a single rise in concentration, while in mammals, the concentration oscillates. This book provides comprehensive insights into the research on calcium signaling. It presents researches and studies performed by experts across the globe. This book will serve as a reference to a broad spectrum of readers.