How are the epithelial tissues classified?

The epithelial tissues are classified according to the shape of the cells that form it (epithelial cells may be cuboidal, columnar, or squamous) and according to the number of layers in which those cells are placed in the tissue (into stratified or simple).

The major types of epithelial tissues are cuboidal, simple, simple columnar, simple squamous, stratified squamous and pseudostratified columnar (resembling more than one layer but actually having only one). There are also stratified cuboidal and stratified columnar epithelia (rare).

The Epithelium - Image Diversity: types of epithelial tissue