So suppose we have a prokaryotic gene and we want to basically obtain many copies of the proteins that are encoded by that specific prokaryotic gene. Well, recombinant DNA technology allows us to basically carry out this process. And what it tells us, Yale, is all we have to do is take that prokaryotic gene, place it into the appropriate vector, then introduce that vector into a bacterial cell. And the bacterial cell will essentially use its ribosomes, its cell machinery to synthesize the proteins that are encoded by that particular gene. And then we can extract and collect and study those proteins from that bacterial cell. Now, what's one application of this method?