H&E stain, or Hematoxylin and Eosin stain, is a widely used technique in histology for examining tissue samples under a microscope. Hematoxylin stains cell nuclei blue, highlighting the genetic material, while Eosin stains the cytoplasm and extracellular matrix pink. This contrast allows pathologists to identify different cell types and structures within tissues. The H&E stain is essential for diagnosing diseases, including cancers, by providing clear visual differentiation of cellular components. It is often the first step in tissue analysis, helping to guide further testing and treatment decisions based on the observed histological features.