Calcium imaging is a microscopy technique that is used to optically measure the calcium status of an isolated cell or tissue. It involves the use of calcium indicators, which are fluorescent molecules. These fluorescent molecules respond to the binding of Ca2+ ions by fluorescence properties.

Calcium imaging is based on the sensitivity of the calcium indicators to changes in specific environmental factors such as pH, pressure, temperature, proximity of other fluorophore species and ionic strength. The variations in calcium concentration at different locations can be studied by measuring the ratio of intensities on digital images captured at precise wavelengths at which the difference in fluorescence emission signals is at a maximum.