The BrdU assay involves several key steps: 1. Labeling: Cells are incubated with BrdU, which gets incorporated into the newly synthesized DNA of dividing cells. 2. Fixation: The cells are fixed to preserve their structure and the incorporated BrdU. 3. Detection: Antibodies specific to BrdU are used to detect its presence. These antibodies can be conjugated with fluorescent tags or enzymes that produce a colorimetric change. 4. Quantification: The amount of BrdU incorporated is quantified using techniques such as flow cytometry or microscopy, indicating the level of cell proliferation.