And that essentially confirmed the fact that after one generation, after one cycle we form one type of DNA molecule that consists of one radioactively labeled strand and one newly synthesized strand that contains the lighter N 14 isotopes. And so this is what we saw. So one of these was N 15 and the other one was N 14 because it was synthesized using the nitrogen atoms that had an atomic mass of 14 and not 15. And because of their lighter nature they're going to be less dense and so they're going to appear farther to the left along that x axis. Now, what do they see after a second cycle of division? So following a second division, a second replication, once we extract the DNA molecules from those cells, this is what we saw.