As we have seen on Figure , materials with two-dimensional topologies represent 9.7% of the Materials Project database, corresponding to 17,577 crystalline structures. Also called "two-dimensional layered materials" (or simply "layered materials"), these materials consist of "sheets" without chemical bonds between them. They are interesting for two main reasons: (i) their layered nature gives rise to specific physical properties, marked by a very strong anisotropy; (ii) they can be considered precursors of truly two-dimensional materials (similarly to the relationship of graphite and graphene).