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. So before crossing over takes place, homologous pairs must find each other and move side by side with respect to each other. And this pairing, this movement of the homologous chromosomes next to one another, is known as synapses. And this is shown in the following diagram.