The article discusses the development and application of carbon dots (C-Dots) as optical imaging agents for in vivo studies. C-Dots, small carbon nanoparticles surface-passivated with organic or biomolecules, are noted for their bright fluorescence, biocompatibility, and stability. Unlike semiconductor quantum dots (QDs), which can be toxic, C-Dots are considered non-toxic even at low concentrations. The study reports the first in vivo imaging of C-Dots in mice, demonstrating their effectiveness as contrast agents. C-Dots were injected subcutaneously, intravenously, and interdermally, showing strong fluorescence and slow diffusion. In vivo imaging revealed that C-Dots primarily excreted through the urine, with minimal accumulation in the liver and kidneys. The results suggest that C-Dots have significant potential for biomedical applications in optical imaging.The article discusses the development and application of carbon dots (C-Dots) as optical imaging agents for in vivo studies. C-Dots, small carbon nanoparticles surface-passivated with organic or biomolecules, are noted for their bright fluorescence, biocompatibility, and stability. Unlike semiconductor quantum dots (QDs), which can be toxic, C-Dots are considered non-toxic even at low concentrations. The study reports the first in vivo imaging of C-Dots in mice, demonstrating their effectiveness as contrast agents. C-Dots were injected subcutaneously, intravenously, and interdermally, showing strong fluorescence and slow diffusion. In vivo imaging revealed that C-Dots primarily excreted through the urine, with minimal accumulation in the liver and kidneys. The results suggest that C-Dots have significant potential for biomedical applications in optical imaging.