Histological techniques such as hematoxylin and eosin (H&E) staining can be used to observe oxyhemoglobin in tissue sections. Hematoxylin stains cell nuclei blue, while eosin stains cytoplasm and extracellular matrix pink. Oxyhemoglobin-rich red blood cells typically appear bright red under the microscope due to their oxygen content. Advanced imaging techniques like fluorescence microscopy and confocal microscopy can also be employed to study oxyhemoglobin distribution.