The polymerase chain reaction (PCR) is a means by which large quantities of a specific segment of DNA can easily be produced (amplified) from very small amounts of “template” DNA in the laboratory in a short period of time. Quantitative polymerase chain reaction (qPCR) is a means of determining the concentration of a DNA solution. Due to its ability to create potentially billions of copies of a targeted portion of a genome, PCR from a small number of template DNA molecules has revolutionized many areas of research and has become a standard procedure in a variety of fields, including clinical diagnostics, preimplantation genetic diagnosis, forensic science, phylogenetic analysis, DNA barcoding, and the study of ancient DNA.