# XNA Veiwing cubes behind others

I am learning 3D at the moment. It is going well but I am stuck on the viewing of the camera.

I have two cubes, one next to each other made up of vertices, all the faces/triangles in the cubes are clockwise vertics so that when you move around the box, only 1 or two sides are visible at once. But, here's the problem, if I look at the cubes from the right, I can see a face of the cube that is further away. Like pictured below,

What would be the best way to deal with this, and are there any tutorials that could help me please?

GraphicsDevice.DepthStensilState = DepthStensilState.Default