Fluo 4-AM is widely used as a fluorescent calcium indicator in biological research. It is particularly valuable for studying intracellular calcium dynamics in live cells. When Fluo 4-AM enters cells, it is hydrolyzed by esterases to Fluo 4, which then binds to calcium ions, resulting in a significant increase in fluorescence intensity. This property makes it an essential tool for real-time imaging and monitoring of calcium signaling in various cell types, including neurons, muscle cells, and immune cells. It is commonly employed in fluorescence microscopy, flow cytometry, and high-throughput screening assays to investigate cellular processes such as signal transduction, cell proliferation, and apoptosis. Its high sensitivity and low photobleaching make it a preferred choice for researchers studying calcium-related physiological and pathological conditions.