The article provides a comprehensive overview of carbon quantum dots (CQDs) and their applications in bioimaging and biomedicine. CQDs, first synthesized in 2004, are submicron-sized nanomaterials with unique properties such as solubility in water, chemical inertness, biocompatibility, and non-toxicity. These properties make CQDs suitable for various applications, including bioimaging and biomedicine. **Synthesis of CQDs:** CQDs can be synthesized using both top-down and bottom-up methods. Top-down methods involve physical or chemical processes that break down larger carbon structures into smaller ones, while bottom-up methods use thermal or chemical reactions to assemble smaller carbon precursors. Common top-down methods include laser ablation, arc discharge, and acidic oxidation, while bottom-up methods include combustion, hydrothermal, microwave, pyrolysis, and template-assisted techniques. **Characteristics and Properties of CQDs:** CQDs exhibit a "core-shell" nanostructure with surface functional groups and a nanoscale carbon core. Their properties, such as absorption spectra, fluorescence emission, and photostability, can be modified through surface passivation and doping. CQDs have a wide range of applications due to their photoluminescence, stability, and biocompatibility. **Applications in Bioimaging:** CQDs are used in bioimaging due to their intrinsic fluorescence, stability, and biocompatibility. They can penetrate various cells through endocytosis and are used for labeling cellular compartments and organelles. CQDs have been successfully applied in intracellular imaging and in vivo imaging, showing high photostability and low cytotoxicity. **Applications in Biomedicine:** CQDs are also used in biomedical applications, particularly in drug delivery and gene therapy. They can be used to deliver drugs to specific sites with minimal side effects and have shown promise in cancer treatment. CQDs can be functionalized with various ligands to enhance their targeting and therapeutic efficacy. Additionally, CQDs have been explored for stem cell biology and photodynamic therapy. **Challenges and Future Directions:** Despite their advantages, CQDs face challenges such as the need for costly ingredients, severe reaction conditions, and extended reaction times. Future research aims to improve the quantum yield, size control, and biocompatibility of CQDs to enhance their performance in various applications.The article provides a comprehensive overview of carbon quantum dots (CQDs) and their applications in bioimaging and biomedicine. CQDs, first synthesized in 2004, are submicron-sized nanomaterials with unique properties such as solubility in water, chemical inertness, biocompatibility, and non-toxicity. These properties make CQDs suitable for various applications, including bioimaging and biomedicine. **Synthesis of CQDs:** CQDs can be synthesized using both top-down and bottom-up methods. Top-down methods involve physical or chemical processes that break down larger carbon structures into smaller ones, while bottom-up methods use thermal or chemical reactions to assemble smaller carbon precursors. Common top-down methods include laser ablation, arc discharge, and acidic oxidation, while bottom-up methods include combustion, hydrothermal, microwave, pyrolysis, and template-assisted techniques. **Characteristics and Properties of CQDs:** CQDs exhibit a "core-shell" nanostructure with surface functional groups and a nanoscale carbon core. Their properties, such as absorption spectra, fluorescence emission, and photostability, can be modified through surface passivation and doping. CQDs have a wide range of applications due to their photoluminescence, stability, and biocompatibility. **Applications in Bioimaging:** CQDs are used in bioimaging due to their intrinsic fluorescence, stability, and biocompatibility. They can penetrate various cells through endocytosis and are used for labeling cellular compartments and organelles. CQDs have been successfully applied in intracellular imaging and in vivo imaging, showing high photostability and low cytotoxicity. **Applications in Biomedicine:** CQDs are also used in biomedical applications, particularly in drug delivery and gene therapy. They can be used to deliver drugs to specific sites with minimal side effects and have shown promise in cancer treatment. CQDs can be functionalized with various ligands to enhance their targeting and therapeutic efficacy. Additionally, CQDs have been explored for stem cell biology and photodynamic therapy. **Challenges and Future Directions:** Despite their advantages, CQDs face challenges such as the need for costly ingredients, severe reaction conditions, and extended reaction times. Future research aims to improve the quantum yield, size control, and biocompatibility of CQDs to enhance their performance in various applications.