Hematoxylin 5 %, alcoholic, is a commonly used histological staining solution for staining cell nuclei in tissue sections and cytological specimens. Hematoxylin is a natural dye obtained from the heartwood of the tropical tree resin Haematoxylum campechianum. In the 5% alcoholic solution, hematoxylin is dissolved in alcohol, which allows faster penetration and staining of tissue.

Hematoxylin binds to the basic components of cell nuclei, especially DNA, and stains them blue-violet. This staining is often used in combination with a counterstain, such as eosin, to better distinguish different cell structures and tissue types.