Haematoxylin 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 microscopy to stain biological tissues, allowing for the visualization of cellular structures under a microscope. Haematoxylin stains cell nuclei a deep blue or purple color, making it easier to identify and study various cell types. In laboratory settings, haematoxylin 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 pathology for examining tissue samples, helping pathologists diagnose diseases and conditions by providing clear images of tissue architecture.