Squamous epithelial cells are flat, scale-like cells that form a type of tissue known as squamous epithelium. This tissue lines various surfaces in the body, including the skin, mouth, and lungs. Their thin structure allows for efficient exchange of substances, making them essential for processes like gas exchange in the lungs. These cells can be classified into two main types: keratinized and non-keratinized. Keratinized squamous cells, found in the skin, provide protection against environmental damage, while non-keratinized cells, found in areas like the mouth and esophagus, help with moisture retention and facilitate absorption.