A microscopic study of epithelial and connective tissues involves using a microscope to examine thin tissue samples at the cellular and subcellular levels. This type of study is commonly conducted in histology and biology labs to understand the structure and function of these essential tissue types in the human body. Epithelial Tissue: Epithelial tissue is one of the four primary tissue types in the human body. It forms the outermost layer of the skin, the lining of organs and body cavities, and the lining of the respiratory, digestive, and urinary systems. During a microscopic study of epithelial tissue, you'll observe the following characteristics.