In Vitro: Guidelines (Following is our recommended protocol. This protocol only provides a guideline, and should be modified according to your specific needs). In vivo: 1. The powdered IR-820 was freshly mixed with phosphate buffer saline (PBS) to a final concentration of 0.2 mM and 100 μl of this solution was used for injecting into experimental animals. 2. Used 2 groups of four Hairless SKHi/sKHl mice. The first group was injected with IR-820 by intravenous tail vein injection while the second was injected intraperitoneally. 3. IR-820 has maximal excitation and emission wavelengths of 710 nm and 820 nm, respectively. Both groups were serially imaged for 8 days.