So gel electrophoresis is the process by which we separate. We use the charge on the protein to move that protein along an electric field, and we basically separate the proteins based on size. So notice that gel filtration chromatography and gel electrophoresis, these two methods both use the size factor. But the major difference between gel electrophoresis and gel filtration chromatography is in gel electrophoresis, all the proteins actually move along that region, while in gel filtration chromatography, the very small proteins essentially are trapped inside the beads of that system, as we'll see in a future lecture. Now, in isoelectric focusing, this is where we separate our proteins based on their isoelectric point. And the isoelectric point is that specific PH value at which the net charge on that protein is essentially neutral, and we'll see exactly is essentially zero, and we'll see exactly what that means once again in a future lecture.