Polymerase Chain Reaction (PCR) is a laboratory technique used to amplify small segments of DNA. It was first developed in the 1980s by Kary Mullis, who was awarded the Nobel Prize in Chemistry in 1993 for his pioneering work. PCR is based on using the ability of DNA polymerase to synthesize a new strand of DNA complementary to the offered template strand. The technique involves using short synthetic DNA fragments called primers to select a segment of the genome to be amplified, and then multiple rounds of DNA synthesis to amplify that segment. The process of PCR involves three main stages: denaturing, annealing, and extending, which are repeated 20-40 times, doubling the number of DNA copies each time. The amplified DNA produced by PCR can be used in many different laboratory procedures, including DNA fingerprinting, detection of bacteria or viruses, and diagnosis of genetic disorders. PCR is a common tool used in medical and biological research labs.