For years, the focus of scientists' research has been the mechanisms that lead to the onset of cancer, as a basis for the further development of diagnostic approaches in its early detection, as well as the development of personalized therapy and increasing the survival rate of patients suffering from cancer. The current gold standard of diagnosis is biopsy of tumor tissue, which has several limitations, and the development of other diagnostic approaches is expanding. In recent years, liquid biopsy has become the center of research in clinical oncology, both because of its non-invasive approach and because it opens the door to a much larger area of investigation than tissue biopsy. The term liquid biopsy refers to the sampling of biological material that does not include solid tumor tissue, such as blood, urine, saliva, cerebrospinal fluid, etc. There are three basic markers of liquid biopsy, circulating tumor cells, circulating DNA and exosomes, which together form a huge area of research that offers enormous progress in the field of diagnosing, monitoring diseases and predicting adequate targeted therapy.