Histological techniques used to study cellular aging include tissue staining, immunohistochemistry, and in situ hybridization. These methods can identify and quantify markers of cellular aging, such as telomere length, senescent cells, DNA damage, and oxidative stress. Advanced imaging techniques, such as electron microscopy, can provide detailed insights into the ultrastructural changes that occur in aged cells and tissues. By combining these approaches, researchers can gain a comprehensive understanding of the cellular and molecular mechanisms underlying aging.