Digital PCR builds on traditional PCR amplification and fluorescent-probe?based detection methods to provide highly sensitive absolute quantification of nucleic acids without the need for standard curves. In the Droplet Digital? PCR System, a PCR sample is partitioned into 20,000 droplets. After amplification, droplets containing target sequence are detected by fluorescence and scored as positive, and droplets without fluorescence are scored as negative. Poisson statistical analysis of the numbers of positive and negative droplets yields absolute quantitation of the target sequence.