And we also radioactively label that DNA primer because that will basically allow us to pinpoint exactly where that molecule is when we undergo the process of gel electrophoresis. So we add a label DNA primer that is complementary to the three end of that single stranded DNA molecule that we want to sequence. So this is the three end of that DNA molecule. And remember, DNA polymerase reads from three to five and it builds from five to three. And that's why this is the end that we actually want to build the DNA primer for. So we add the DNA polymerase and we also add the four types of deoxy nucleus diet triphosphate.