The trypan blue exclusion test is a simple laboratory method used to assess cell viability. In this test, cells are mixed with a blue dye called trypan blue. Live cells exclude the dye and remain clear, while dead cells take up the dye and appear blue. This allows researchers to easily distinguish between viable and non-viable cells under a microscope. This test is commonly used in various fields, including cell biology and pharmaceutical research, to evaluate the health of cultured cells. It helps scientists determine the effectiveness of treatments or the quality of cell samples before further experimentation.