The concept of the “Marine M Carbonate Factory” was proposed nearly two decades ago, yet its definition remains ambiguous, its controlling factors highly variable, and the origin of its primary components—micrites complex and debated. Various terminologies—such as the “mud mound” factories, the “automicrite” factories, the “microbialite” factories, and the “cold- seep” carbonate factories—overlap and intertwine, further complicating the classification. To advance research on carbonate factories, there is an urgent need to clarify their conceptual framework, standardize their classification, and synthesize their controlling factors and genetic origins. Based on extensive literature review, this paper systematically examines the proposal, evolution, and unresolved issues surrounding the Marine “M” Carbonate Factory concept. It summarizes the possible sources of carbonate micrite within marine carbonate factories and proposes a refined classification scheme. Conclusions: The “Marine M Carbonate Factory” is categorized into two major groups with six subclasses: ① Euphotic Zone Microbialite Factories (further divided into skeletal microbialite factories and non- skeletal microbialite factories); ② Mesophotic-/Aphotic Zone Mud Mound Factories (subdivided into automicritic mud mound factories and allomicritic mud mound factories). The automicritic mud mound factories can be further classified into: ① Heterotrophic automicritic carbonate factory; ② Cold- seep automicritic carbonate factory; ③ Hydrothermal automicritic carbonate factory. Finally, this paper offers perspectives on the transitions between different categories within the M carbonate factories in marine settings and their transitions with other carbonate factories, as well as on the microbial loop and sponge loop within M carbonate factories during the microbial—metazoan transition period.