So, in the absence of ADH, we don't have any of these aquaporeans on the apical membrane. All these aquaporn channels are found inside these vesicles. They're stored inside these vesicles. Now, if we look at diagram B, now we're basically adding our ADH in the presence of ADH antidiauretic hormone stimulates the transfer of these aquaporeans from these storage vesicles and into the membrane on the apical side of the cell. And now, because we have these aquaporeans, water can easily travel from a low solub concentration inside the lumen to the outside of our cell, on the other side, our surrounding tissue, known as the interstituum. So this is the method by which ADH acts on our collecting dust and forces it to absorb more water.