The constant-pressure first-principles molecular dynamics (CP-FPMD) method shows its great power in the investigation of high-pressure phenomena which are difficult to observe in experiments. In this article, I present a survey of this CP-FPMD method as well as a new technique we developed for the determination of transition states. I also illustrate their ability with our investigations of high-pressure synthesis of BCN heterodiamonds and pressure induced metallization of organic monomolecular crystals.