Luminescent carbon nanoparticles represent a new class of photoluminescent nanomaterials. Growing interest in these nanoparticles stems from straightforward methods of their synthesis, a wide variety of available precursors, the lack of toxicity, photo stability and simple surface modification for further application. Due to low cytotoxicity and tunable optical properties of carbon nanoparticles, they are used in various fields of biology and medicine. At the same time, current application of carbon nanoparticles is limited by the lack of understanding of the fundamental relationship between their structure and properties. The review focuses on the latest trends in the synthesis, study of the structure, composition and properties of carbon nanoparticles and on their biomedical applications.