BrdU (Bromodeoxyuridine) is used extensively in cell proliferation assays.

Bromodeoxyuridine (BrdU) is a thymidine analog. BrdU gets incorporated into the DNA of dividing cells during the S-phase of the cell cycle. It is used for birth dating and for identifying and monitoring proliferating cells. BrdU immunohistochemistry has played a key role in studying the development of the nervous system, and establishing that neurogenesis occurs in the adult mammalian brain. BrdU can also be used to identify microorganisms that respond to specific carbon substrates in aquatic and soil environments.