And so the proteins move along the tube and through the beads. And the proteins that are largest will move fastest along the test tube. And the ones that are smallest, because they get trapped inside those beads, they will move the slowest. Now, in ion exchange chromatography, we separate our proteins based on their charge in affinity chromatography, this is where we basically separate our protein based on its affinity, on its ability to attract itself to specific types of other molecules. So in our tube, we can basically form these different types of specific molecules along the tube. And as the proteins are allowed to move along the tube, those proteins that do bind or are attracted to those molecules will bind to the surface of our tube.