because there is no backscattering of a chiral electron off the considered potential preserving the sub-lattice state. For that very reason as well, we do not see the linear temperature dependence of resistivity. Graphene presents a planar sheet structure composed of sp 2hybridized carbon atoms. The single electrons left on the p atomic orbitals of each carbon atom form a system of conjugated π bonds. Here, we would like to stress its connection to graphene conductivity. From the chemical standpoint, the zone theory valence bands and conduction bands in graphene are formed from π and π * states, respectively . This means that the "metallic" in-plane conductivity of graphene may be attributed to the strong conjugation of π orbitals. The connection between the FOs and conjugation is discussed in more detail in the section 4 of this review.