The present application relates to a continuous droplet flow microfluidic system, including a microfluidic chip including an optical detection section; a stage assembly including a microfluidic chip holder configured to receive the microfluidic chip and a plurality of heating elements arranged to heat a plurality of separate sections of the microfluidic chip to a corresponding plurality of different temperatures; and an optical detection system arranged to detect fluorescent light emitted from said optical detection section of the microfluidic chip.