I wanted to show how Morh's Circle: Each " dot " represents a different plane of the Cube. If you just draw the circle, it's hard to picture that each " dot " is in a different plane. Here you can see the approximate orientation of the principle stresses perpendicular to the principle shears. And of course you have to draw in the rest of Morh's Circle, but now you can see the planes associated with the stress and shear.
I always had trouble picturing Morh's Circle, hopefully this helps with that picture.