The Incucyte® Nuclight Rapid NIR Dye 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 Dye 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 Dyes for simultaneous readouts of apoptosis or cytotoxicity alongside cell proliferation. The Incucyte® Nuclight Rapid NIR Dye has been validated for use with Incucyte® Live-Cell Analysis Systems configured with an Orange/NIR Optical Module or a Green/Orange/NIR Optical Module.