The column is packed with these charge gel beads. And depending on the proteins that we actually want to separate, we can make those beads either positively charged, as in this case, or negatively charged, as in this particular case. So red means positively charged, and blue means negatively charged. And these beads are usually made from some type of carbohydrate polymer, such as cellulose. Okay, so in this lecture, we're going to focus on this setup. So let's zoom in on one of these, or let's zoom in on a small section of our column.