Cold seeps are seafloor manifestations of methane-rich fluid migration from the sedimentary subsurface to the seabed and into the water column, and ultimately, some of the methane may even reach the atmosphere (Boetius and Wenzhöfer 2013). Marine hydrocarbon seeps are common features of continental margins worldwide (Suess 2020). Because of their relevance for oceanic emissions of the greenhouse gas methane, widespread chemosynthesis-based ecosystems, and their spatial overlap with areas containing gas hydrate, hydrocarbon seeps have been considered ideal natural laboratories for studying Earth’s mass and energy cycling from the geosphere to the exosphere (Boetius and Wenzhöfer 2013; Suess 2020). The term “??”(the term “cold seep” in Chinese) was first introduced by Duofu Chen and his colleagues in 2002, as published in the first issue of the journal Acta Sedimentologica Sinica (Fig. 1.1). Since then, great progress has been made in regard to the hydrocarbon seeps in the South China Sea (SCS). To date, various types of samples, including authigenic minerals, seep-impacted sediments, and seep fauna, have been recovered from more than 40 seep sites, which cover a wide range of water depths in both the northern and southern continental margins of the SCS.