This article will briefly review 2D electronics. First, the most commonly seen 2D materials will be introduced,including Group IV elements(C, Si, Ge, and Sn), phosphorus, and transition metal dichalcogenides TMDs. Their crystal structures, band structures, and bandgaps will be explained. The most commonly studied 2D field-effect transistors (2D FETs) composed of silicene, graphene, MoS2 and WSe_2 will be introduced and explained. The reason of using 2D FETs will be explained in terms of the evolution of field-effect transistors. Finally is the summary.