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. But the ones that don't, the proteins that don't will essentially move straight down along our tube. And we'll discuss that in much more detail in the next hour of electros. Now, gel electrophoresis is something we spoke about already in biology.