Our columnar simply means we have these rectangular like columns and C squamous simply means our cells are very flat so they look something like this. Now, these cells can basically organize themselves to form our epithelial tissue or the epithelium. And epithelium can be organized in three different ways. We can have simple epithelium, we can have stratified epithelium and we can also have something known as pseudostratified epithelium and we'll see what that means in just a moment. First, let's discuss simple and stratified epithelium. Now, a simple epithelium means that we have a single layer of cells across the entire basement membrane and we'll see what the basement membrane is in just a moment.