It contains these tiny holes, these tiny pores, and that allows small molecules to pass through those tiny pores. So this is our setup. We have the funnel inside. The funnel is placed on top of our column, and inside the column, we have these pores gel beads. And so, as our fluid flows along our gel beads, that water doesn't actually dissolve our beads. So those beads are in soluble, but things can actually pass across those beads as a result of those tiny pores.