Calcium signaling is a step in signal transduction that makes use of calcium ions to communicate and drive intracellular processes. Calcium ions play an important role in cellular signaling because when they enter the cytosol of the cell, they exert allosteric effects on many enzymes and proteins. The resting concentration of calcium ions in the cytoplasm is 100 nM and this is much lower than the extracellular concentration. Calcium ions are continuously pumped from cytosol to extracellular space to maintain this low concentration. Cell signaling occurs when the cell releases calcium ions from intracellular stores, and when calcium ions enter the cell via the ion channels present in the plasma membrane. The aim of this book is to present recent researches in the field of calcium signaling. It includes some of the vital pieces of work being conducted across the world, on various topics related to calcium signaling. This book will help new researchers by foregrounding their knowledge in this branch.