Calcein-AM是一种可对活细胞进行荧光标记的细胞染色试剂，Calcein-AM由于在Calcein的基础上加强了疏水性，因此能够轻易穿透活细胞膜。当其进入到细胞质后，酯酶会将其水解为Calcein留在细胞内,发出强绿色荧光。与其它同类试剂（如BCECF-AM和Carboxy-fluorescein diacetate）相比，Calcein-AM是最适合作为荧光探针去染活细胞的，因为它的细胞毒性很低。Calcein不会抑制任何的细胞功能如增殖或淋巴球的趋化性。另外，使用了Calcein的活性检测的实验结果是十分可信并且与标准的⁵¹Cr-释放法所得结果相一致的。Calcein的激发和发射波长分别为496  nm和516  nm。

Calcein-AM is a hydrophobic non-fluorescent probe that can permeate the plasma membrane and can be hydrolyzed to Calcein, which is an extremely fluorescent and negatively charged molecule. The probe can be used to stain living cells and has been observed to fluoresce bright green in cytoplasmic Schwann cells. Calcein-AM has been reported to be a neutral substrate for Mdr (P-glycoprotein (Pgp) and multidrug resistance protein (MRP)) and has been used in flow cytometry studies to analyze the function of P-gp and MRP. Studies suggest that Calcein-AM can be used to detect MDR mediated resistance and to be transported by PGP from the plasma membrane. Mitochondrial permeability research has utilized Calcein as a cytosolic fluorophore. Has been used as a cytosolic fluorophore in mitochondrial permeability studies to image pore transition.