Quantitative PCR, or qPCR, is a laboratory technique used to amplify and quantify DNA. It allows scientists to measure the amount of a specific DNA sequence in a sample, providing insights into gene expression, pathogen detection, and genetic variations. The process involves repeated cycles of heating and cooling, which help to separate the DNA strands and replicate them. During qPCR, a fluorescent dye or probe is used to monitor the amplification of DNA in real-time. As the DNA is copied, the fluorescence increases, allowing researchers to determine the initial quantity of the target DNA. This method is widely used in research, clinical diagnostics, and forensic science.