Calcium signaling is a crucial process in cells that involves the movement of calcium ions (Ca²⁺) across cell membranes. When a cell receives a signal, such as a hormone or neurotransmitter, it can trigger the release of calcium from internal stores or allow calcium to enter from outside the cell. This increase in calcium concentration acts as a messenger, influencing various cellular activities like muscle contraction, neurotransmitter release, and gene expression. The effects of calcium signaling are diverse and depend on the specific cell type and context. For example, in muscle cells, calcium ions are essential for contraction, while in neurons, they play a key role in transmitting signals. Proper regulation of calcium levels is vital for maintaining cellular health and function.