This is a slide of a thin section taken from the mammalian kidney showing the many tubular ducts that make up much of this organ. The walls of these ducts (pointed to by the red arrows) are comprised of simple cuboidal epithelial cells, which are usually six-sided in shape but may appear square from a side view.  Note also the thin wall of simple cuboidal epithelium (pointed to by the blue arrow) that forms the top edge of this section.