So, in the same way that to actually create a cell, we have to begin with a cell, to create a membrane, we have to begin with the membrane. So when we're building our cell membrane, we build it by essentially expanding the preexisting membrane. And that preexisting membrane basically was asymmetric to begin with. So we see that, in addition, asymmetry is also preserved because membranes always arise and grow and extend from preexisting membranes, which are asymmetric to begin with. Now, in our discussion here, we said that the difference in the composition of not only the proteins but also the lipids basically gives this membrane the property of asymmetry. So now let's move on from proteins to lipids.