Now, at the same exact time, the chromatin condenses into the chromosomes and the nuclear membrane, as well as our nucleolus, begins to disappear. And that's exactly what allows our spindle fibers to make its way into the nucleus area of our cell. Now, the major difference between ProPhase one of meiosis and ProPhase of mitosis is the following. So the major process that takes place within ProPhase one is a type of genetic recombination process known as crossing over. And we'll see what crossing over is in just a moment. Now, before crossing over actually takes place, our two homologous pairs of chromosomes actually have to find one another and basically orient themselves side by side, and then that allows crossing over to actually take place.