A method for replicating specific sequences of DNA which is capable of forming millions of copies in hours. First, sample dsDNA is denatured (at ~95°C); then primers bind (at ~45°C) to each strand such that 5' to 3' extension of primers will copy the target region. Finally, elongation of strands occurs at around 72°C (this temperature depends on which thermostable polymerase is used) . this cycle is repeated several times as needed.