So we have these tiny pores inside our bag. And these tiny pores allow the movement of very small molecules and ions, but prevent the movement of large molecules such as protein. So, inside the bag, we have this solution, where we have these protein molecules shown in purple, and these very tiny molecules shown in red. So the membrane can be, for example, composed of cellulose, and it contains very tiny pores. Now, what happens if we take this bag? We're going to call our dialysis bag and place it into our solution of pure water.