Western blotting (protein immunoblotting) is used to detect and identify specific proteins in a sample. The process: SDS-PAGE separates proteins by size → transfer to nitrocellulose/PVDF membrane → blocking → incubation with primary antibody (specific to target protein) → secondary antibody (enzyme-conjugated) → substrate → visualisation. Compare: Southern blotting = DNA; Northern blotting = RNA; Western blotting = Protein.