5-bromodeoxyuridine (BrdU) is a synthetic nucleoside that is a derivative of deoxyuridine. It is commonly used in molecular biology and cancer research to study cell proliferation. BrdU can be incorporated into DNA during the S-phase of the cell cycle, allowing researchers to track dividing cells. In laboratory settings, BrdU is often detected using specific antibodies in techniques like immunohistochemistry or flow cytometry. This helps scientists visualize and quantify the rate of cell division in various tissues or tumors, providing insights into cellular processes and the effects of treatments on cancer cells.