Now, what happens in ProPhase is these two centriots begin to move to opposite ends as shown in the following diagram. And as they move to opposite ends the centrioles begin to synthesize the spindle apparatus also known as the mitotic spindle apparatus. And what the mitotic spindle apparatus consists of is special types of spindle fibers that are made from microtubules. So as our two centrioles move apart to opposite ends of the cell to opposite poles of the cell our microtubules, the spindle fibers, also known as asters, begin to grow and they radiate outward towards the center of our cell, towards our nucleus. At the same time that happens our nuclear membrane begins to deteriorate and the nucleolus disappears altogether. And what this basically does is it allows the spindle fibers to make its way into the nucleus region of our cell so that our spindle fibers, as we'll see in just a moment can actually attach to a special region on the centromere.