Abstract The electrical interfacing of individual nerve cells and semiconductor microstructures as well as the assembly of neuronal networks and microelectronic circuits, is considered. At first the planar core–coat conductor of a neuron–silicon junction is studied as it determines the coupling of ion-conducting neurons and electron-conducting silicon. The width of the cleft between cell and chip, the resistance of cleft and voltage-gate ion channels in the junction are investigated. On that basis, a subsequent section describes the electronic interfacing of individual cultured neurons with silicon microstructures as well as the integration of microelectronics with small neuronal networks grown in culture. In a final part, the electronic interfacing of cultured brain slices is addressed. The goal of this approach is an integration of neuronal network dynamics and digital computation on a microscopic level for studies in brain research, biosensorics, information technology and medical prosthetics.