Well, not only does the polarity determine the ability, the permeability of that molecule, but also the size and the concentration also determine its ability to actually pass across the cell membrane. So water molecules are actually relatively small molecules and they can squeeze across the cell membrane with ease. On top of that, if we discuss the polarity of the water molecule and we compare it to, let's say, the tryptophan or this potassium, the tryptophan and potassium actually have full charges. And so they're much more polar than water. So because water does not actually have a full charge, it can pass across the cell membrane with ease. On top of that, we have many, many water molecules on the outside and inside of that bilayer membrane.