This document discusses the staining of histological slides. It explains that stains are used to provide color contrast under the microscope and stain tissues and cells without depositing dye particles. The most common staining technique is hematoxylin and eosin staining. Hematoxylin stains cell nuclei blue while eosin stains cytoplasm and other tissue components pink or red. The staining procedure involves deparaffinizing, hydrating, and staining tissue sections, followed by dehydration and mounting of the stained slide.