Brilliant cresyl blue is widely used in biological and medical research as a vital stain. It is particularly effective in staining reticulocytes, which are immature red blood cells, allowing for their identification and counting in blood samples. This application is crucial in diagnosing and monitoring conditions like anemia and bone marrow function. Additionally, it is utilized in microbiology to stain live cells, helping differentiate between viable and non-viable cells in various studies. The dye also finds application in histology for staining specific tissue components, aiding in microscopic examination and analysis.