With the development of the quantitative PCR detection methodologies, different types of PCR techniques have been developed, such as real-time quantitative PCR, competitive real-time PCR, etc. However, all the above techniques only achieve quantitative detection by standard curves and are considered labor-intensive experiments. Based on this background, digital PCR (dPCR), an absolute quantitative detection method, was developed in the 1990s and could achieve quantitative detection without the generation of standard curves. The idea of digital PCR was first raised by Kinzler and Vogelstein in the 1990s based on the limited separation of the original PCR reaction. Digital PCR has the advantage of being highly sensitive, specific, and well stable and having absolute quantitation compared to the original real-time PCR. Over nearly three decades, digital PCR has achieved wide usage in different areas, such as clinical diagnostics, GMO detections, biosensor detections, etc. In this chapter, the background of the development of digital PCR, the concept of digital PCR, and the use of digital PCR in different areas are reviewed in detail. By reading this chapter, the reader could have a better comprehension of all the aspects of digital PCR.