There are three phases of PCR amplification: exponential, linear, and plateau. The exponential phase is the first phase of PCR amplification. Reaction components are in excess, there is an exact doubling of product each cycle, and the reaction is specific and precise. Real-Time PCR measures the Cq value at this phase of PCR. The linear phase is the second phase of PCR amplification. The reaction components are being consumed, amplification slows, and the reactions become highly variable. The final phase of PCR amplification is the plateau phase. The reaction is complete and no more products are being generated. Traditional PCR takes its measurements during this phase of PCR.