Haematoxylin (HMT)

Haematoxylin is a compound extracted from the heartwood of the logwood tree. Hematoxylin is a basic / positive compound that binds to and forms salts with acidic, or basophilic, compounds containing negative charges (such as DNA and RNA which are acidic/negative because the nucleic acid building blocks that come off the phosphate backbone are negatively charged) and stains them dark blue or violet.