What is droplet digital PCR?

Droplet Digital PCR (ddPCR) is a method for performing digital PCR where a sample is partitioned into thousands of nanoliter-sized droplets. Each droplet contains either zero or one (or more) copies of the target molecule. PCR amplification occurs within each droplet, and after PCR, each droplet is read as either positive or negative for the target sequence. This allows for absolute quantification of the target DNA or RNA without the need for external standards. It is commonly used for applications such as rare mutation detection, copy number variation analysis, and gene expression quantification.