ION Calcium Red – 1 (ICR-1) is a red fluorescent (Ex/Em 580nm/660nm) calcium (Ca²⁺) indicator for intracellular Ca²⁺ measurements. ICR-1’s long-wavelength emission and a large Stokes shift reduces contributions of autofluorescence, making ICR-1 AM optimal for cellular and tissue imaging applications. ICR-1 can also be multiplexed with GFP-labeled cells or other green fluorophores commonly used in experiments. Unlike some other red fluorescent Ca²⁺ indicators, ICR-1 does not accumulate in the mitochondria. Data supporting fluorescence lifetime imaging and multiphoton imaging capabilities have also been demonstrated.