Trypan red is primarily used in biological research as a vital stain to distinguish between living and dead cells. It is commonly applied in cell viability assays, where it helps researchers assess the health and integrity of cell cultures. The dye penetrates damaged or dead cells, staining them red, while viable cells remain unstained. This property makes it a valuable tool in studies involving cytotoxicity, drug screening, and tissue engineering. Additionally, Trypan red has been historically used in parasitology to study and identify trypanosomes, the causative agents of diseases like sleeping sickness. Its staining capabilities provide a quick and effective method for visualizing cellular structures and assessing experimental outcomes.