Thionin acetate is widely used as a biological stain in microscopy, particularly for highlighting cellular components in tissues. It is effective in staining nucleic acids, making it valuable for visualizing chromosomes and DNA in cytogenetic studies. Additionally, it is utilized in histology to differentiate between various tissue structures, aiding in the identification of abnormalities. Beyond microscopy, thionin acetate is employed in neuroscience research to stain brain sections, helping to map neural pathways and study brain morphology. Its staining properties also make it useful in electrophoresis for detecting nucleic acids in gels. Furthermore, it has applications in photodynamic therapy research due to its light-sensitive characteristics, which can be harnessed for targeted cell damage.