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, including simple squamous, simple cuboidal, and simple columnar, each serving specific functions in the body. This tissue is found in various locations, such as the lining of blood vessels, alveoli 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.