The polymerase chain reaction (PCR) method is a quick way to amplify a small sample of DNA using oligonucleotides and the enzyme DNA polymerase. This method, which was invented in the 1980s, is the leading technique for copying and analyzing the quantification of genetic material. Polymerase chain reaction is used in disease detection, forensic science, and genetic research. Since this technique is so popular in modern science, it is important to understand the history and mechanics of PCR, therefore this review details the invention of PCR, how it works today, and some PCR methods including real-time and digital PCR.