Histological stains are chemical dyes used to enhance the contrast of tissue samples under a microscope. These stains help to differentiate between various cellular components, making it easier to identify structures such as nuclei, cytoplasm, and extracellular matrix. Common stains include Hematoxylin and Eosin (H&E), which highlight cell nuclei in blue and cytoplasm in pink. Different stains target specific tissue features, allowing for detailed analysis of biological samples. For example, Gram stain is used in microbiology to classify bacteria, while Masson's trichrome stain helps visualize connective tissue. These techniques are essential in research and clinical diagnostics.