Used as a pH indicator in cell culture media to monitor acidity changes. Turns yellow below pH 6.8, red at neutral pH (around 7.4), and pink to purple above pH 8.2. Commonly added to liquid media for mammalian cell cultures to visually confirm proper pH balance during incubation. Also used in microbiological assays and water quality testing where color change helps detect metabolic activity or contamination. Stable under sterilization conditions, making it suitable for use in autoclaved media.