The electrode array is a device for making multiple electrical contacts with cellular tissue or organs. The electrode array includes a base (1), a two dimensional array of conducting protuberances (2) arising from the base and serving as electrodes, and conductors (3) embedded onto the base and connected to such protuberances for transmitting electrical signals to and/or from the protuberances. The protuberances may also include an insulating layer (15) which covers either the entire protuberance or which leaves the tips exposed for making focused electrical contact. Electrode arrays may be used used singly or in combination with a second electrode array so as to form a sandwich around a target tissue. The sandwich electrode array (16, 17) may employ indexing cones for aligning the opposing electrode arrays and for limiting their vertical proximity. The conductors of the electrode array may be electronically connected or coupled to processing circuitry which amplifies and analyzes the signal received from the tissue and/or which generates signals which are sent to the target tissue and possibly coordinates the generated signals with signals which originate with the tissue.