The IncuCyte® NucLight Rapid NIR Reagent for nuclear labeling is a cell permeable DNA stain that specifically stains nuclei in cells and is ideally suited to the mix-and-read, real-time quantification using the IncuCyte® Live-Cell Analysis System. Addition of the IncuCyte NucLight Rapid NIR Reagent to normal healthy cells is non-perturbing to cell growth and morphology and provides homogeneous staining of nuclei, enabling the real-time, fluorescent quantification of cell proliferation. When added to cell culture medium, the inert stain crosses the cell membrane and has excellent specificity for DNA without the need for a wash step. With the IncuCyte® integrated analysis software, fluorescent objects can be quantified and background fluorescence minimized. This reagent can be multiplexed with IncuCyte® Annexin V, Caspase-3/7 or Cytotox Reagents for simultaneous readouts of apoptosis or cytotoxicity alongside cell proliferation. The IncuCyte NucLight Rapid NIR Reagent has been validated for use with IncuCyte® Live-Cell Analysis Systems configured with an Orange/NIR Optical Module.