hematoxilineosin

Hematoxylin and eosin staining, commonly abbreviated as H&E, is the most widely used staining method in light microscopy for examining tissue sections. It employs hematoxylin to color cell nuclei blue to purple and eosin to stain cytoplasmic and extracellular components pink, producing a high-contrast view of tissue morphology.

Hematoxylin is a basic dye derived from logwood. In practice it is oxidized to hematein and forms a colored complex with a metal mordant, typically aluminum, to create a hematein–aluminum complex. This complex binds preferentially to anionic sites, highlighting nucleic acids and other basophilic structures in blue.

Eosin is an acidic dye that binds to positively charged, eosinophilic structures such as cytoplasm, collagen, and red blood cells, producing pink to red hues. The combination allows simultaneous visualization of nuclei and cytoplasmic or extracellular elements, aiding assessment of tissue architecture and cellular detail.

Procedure: For paraffin-embedded sections, slides are deparaffinized and rehydrated, stained with hematoxylin (often with a bluing step in alkaline solutions), briefly differentiated, rinsed, then counterstained with eosin. After dehydration and mounting, the slide is ready for microscopic examination. Staining conditions vary by protocol.

Applications and limitations: H&E is the standard initial stain in diagnostic pathology and basic histology, enabling assessment of tissue organization, cell morphology, and pathology. It is non-specific; many components require special stains or immunohistochemistry for definitive identification, and staining quality depends on fixation, pH, and timing.

Safety and handling: Reagents are hazardous and require appropriate handling and disposal according to laboratory guidelines, with attention to user safety and environmental considerations.