Reverse transcription quantitative polymerase chain reaction, or RT-qPCR, is a laboratory technique used to measure the amount of specific RNA in a sample. It begins with reverse transcription, where RNA is converted into complementary DNA (cDNA) using the enzyme reverse transcriptase. This cDNA serves as a template for the quantitative polymerase chain reaction, which amplifies the DNA to detectable levels. During the qPCR phase, fluorescent dyes or probes are used to monitor the amplification process in real-time. This allows researchers to quantify the initial amount of RNA in the sample by measuring the fluorescence intensity, providing valuable insights into gene expression and other biological processes.