Cell Proliferation Dye eFluor® 670 is a red fluorescent dye that can be used to monitor individual cell divisions. This fluorescent dye binds to any cellular protein containing primary amines, and as cells divide, the dye is distributed equally between daughter cells that can be measured as successive halving of the fluorescence intensity of the dye. Up to 6 generations may be visualized. Cell Proliferation Dye eFluor® 670 can also be used for long term tracking of labeled cells. Analysis using two-parameter plots may provide better resolution of each generation, especially between undivided cells and the first generation. Cells labeled with Cell Proliferation Dye eFluor® 670 may be fixed and permeabilized for analysis of intracellular targets using standard formaldehyde-containing fixatives and saponin-based permeabilization buffers, such as the Foxp3 Staining Buffer Set (cat. 00-5523) or the IC Fixation Buffer (cat. 00-8222) and Permeabilization Buffer (10X) (cat. 00-8333). Cell Proliferation Dye eFluor® 670 has a peak excitation of 647 nm and its emission can be detected with filter sets used for APC or Alexa Fluor® 647/eFluor® 660 (660/20 bandpass filter or equivalent), making it compatible with applications that utilize GFP. Cell Proliferation Dye eFluor® 670 has a molecular weight of 792.6 and is supplied as a lyophilized powder. Each vial may be reconstituted to a stock concentration of 5 mM with 126 uL of anhydrous DMSO once reconstituted it should be protected from light and stored at -20°C with dessicant. It is recommended to use the reconstituted dye within 6 months and to avoid freeze-thawing.