So one DNA primer binds to the three end of one strand and the other primer binds to the three end of the complementary strand. So now we increase the temperature to about 74 degrees Celsius or 72 degrees Celsius. And the reason we increase it to 72 degrees Celsius is because that is the optimal temperature of the heat resistant DNA polymerase molecule. So we have the deoxyribonucleocide triphosphates and we have that heat resistant DNA polymerase that are found in solution and which are swimming around this DNA molecule. And once we increase the temperature to 72 degrees Celsius, it's then that the DNA polymerase will bind onto the DNA and will begin adding those deoxyribonucleotide triphostate molecules and will begin to synthesize elongate that DNA. And so at the end of step number three, what we have formed is two identical copies of that DNA that we begin with.