In Vitro: Preparation of CFDA-SE working solution 1.1 Preparation of the stock solution Dissolve 1 mg of CFDA-SE in 0.1794 mL of DMSO to obtain 10 mM of CFSE. Note: It is recommended to store the stock solution at -20 ℃ or -80 ℃ away from light and avoid repetitive freeze-thaw cycles. 1.2 Preparation of CFDA-SE working solution Dilute the stock solution in serum-free cell culture medium or PBS to obtain 5-10 μM of CFDA-SE working solution. Note: Please adjust the concentration of CFDA-SE working solution according to the actual situation. Cell staining 2.1 For suspension cells: Centrifuge at 1000 g at 4℃ for 3-5 minutes and then discard the supernatant. Wash twice with PBS, 5 minutes each time. For adherent cells: Discard the cell culture medium, and add trypsin to dissociate cells to make a single-cell suspension. Centrifuge at 1000 g at 4℃ for 3-5 minutes and then discard the supernatant. Wash twice with PBS, 5 minutes each time. 2.2 Add 1 mL of CFDA-SE working solution, and then incubate at room temperature for 30 minutes. 2.3 Centrifuge at 400 g at 4℃ for 3-4 minutes and then discard the supernatant. 2.4 Wash twice with PBS, 5 minutes each time. 2.5 Resuspend cells with serum-free cell culture medium or PBS, and then detect by fluorescence microscope or flow cytometer.