Simple epithelium is a type of tissue that consists of a single layer of cells. This structure allows for efficient absorption, secretion, and filtration. Simple epithelium can be classified into different types based on the shape of the cells, including simple squamous, simple cuboidal, and simple columnar. This tissue is found in various locations throughout the body, such as the lining of blood vessels, air sacs in the lungs, and the digestive tract. Its thinness facilitates the exchange of materials, making it essential for processes like gas exchange and nutrient absorption.