A thermal cycler is a laboratory instrument used to amplify and/or sequence nucleic acids. It works by repeatedly heating and cooling samples in a process called thermal cycling. The cycler is programmed to change the temperature of the samples at specific intervals, allowing for the denaturation, annealing, and extension of DNA strands. Thermal cyclers are used in PCR (polymerase chain reaction) and qPCR (quantitative PCR) experiments, as well as sequencing reactions.