The term algal-mat that is traditionally used in long time was changed into the term microbial mat and was widely adopted, which is resulted from the conceptual transformation of the blue—green algae that should be grouped into cyanobacteria. Long-time researches and studies indicate that the microbial mat is actually a complex microbial community, and this microbial community is actually a consortium of varied kinds of symbiotic/syntrophic organisms that embrace all metabolic pathways that ever emerged on the Earth. Although there are some disagreements, an important idea that carbonate stromatolites were the constructs of algae mats (microbial mats) urges sedimentologists to seek the imprint of microbial activities in terrigenous clastic rocks. The reinterpretation for some problematic trace fossils that were found in the early times results in emergence of some new concepts such as the mat ground and the matground structure.