Polymerase Chain Reaction (PCR) - method to generate millions of copies of a DNA sequence.
PCR uses thermal cycling, with repeated cycles of heating and cooling. Heat physically separates the two strands in the DNA double helix, and lower temperatures each strand is used as a template.
Primers (short DNA fragments) with sequences complementary to the target region along with DNA polymerase allow for repeated amplification. As PCR progresses, the DNA generated is used as a template for further replication allowing for exponential replication.