Hematoxylin is a natural dye derived from the heartwood of the haematoxylon campechianum tree, commonly known as the logwood tree. It is primarily used in histology and pathology to stain biological tissues, allowing for the visualization of cellular structures under a microscope. Hematoxylin stains cell nuclei a deep blue or purple color, making it easier to identify and study various cell types. In laboratory settings, hematoxylin is often used in combination with eosin, another dye that stains the cytoplasm and extracellular matrix. This combination, known as H&E staining, is a standard technique in tissue examination, helping pathologists diagnose diseases by providing clear images of tissue architecture and cellular details.