(A) Four intracellular recordings are depicted: glass micropipette, metal or carbon micro/nanoelectrode, glass micropipette, and nanoFET (from left to right). The green arrows indicate the current flows. (B) and (C) are the equivalent circuits of the intracellular junctions established through conventional devices and nanoFET, respectively. Abbreviations: Cj, junction capacitance; Cm, membrane capacitance; Rs, series resistance; Rj, junction resistance; Rm, membrane resistance; Vm, intracellular potential.