Cells with active caspases can be detected. BD Pharmingen™ Blue Live Cell Caspase Probe contains a fluorochrome-labeled caspase inhibitor. Fluorochrome-labeled caspase inhibitors have three functional domains: fluorochrome , 3-amino acid sequence (VAD) that binds to the active site of the activated caspase, and fluoromethyl ketone (FMK) moiety that allows the probe to irreversibly bind the active caspase.