Haematoxylin or hematoxylin (/ˌhiːməˈtɒksɪlɪn/), also called natural black 1 or C.I. 75290, is a compound extracted from heartwood of the logwood tree (Haematoxylum campechianum) with a chemical formula of C
16H
14O
6. This naturally derived dye has been used as a histologic stain, as an ink and as a dye in the textile and leather industry. As a dye, haematoxylin has been called palo de Campeche, logwood extract, bluewood and blackwood. In histology, haematoxylin staining is commonly followed by counterstaining with eosin. When paired, this staining procedure is known as H&E staining and is one of the most commonly used combinations in histology. In addition to its use in the H&E stain, haematoxylin is also a component of the Papanicolaou stain (or Pap stain) which is widely used in the study of cytology specimens.
