1. A device for stimulating biological tissue, the device comprising: an biocompatible unit including a fluid-impenetrable shaft extending along a longitudinal axis from a proximal end to a distal end, the shaft defining a hollow therein, the hollow being electrically-isolated from an ambient medium surrounding the shaft; a plurality of electrical conductors extending along the longitudinal axis of said unit; at least one microcoil system having a microcoil characterized by a microcoil axis, a longitudinal extent along the microcoil axis, and a diameter, the at least one microcoil system being housed in the hollow at a first distance from the distal end such as to define an angle between the microcoil axis and the longitudinal axis, and a coupling configured to electrically connect the at least one microcoil system through at least one electrical conductor to a power source to define an electrically-closed circuit enabled to drive the at least one microcoil to produce magnetic fields suitable for performing stimulation of neuronal tissue, wherein the at least one microcoil system further comprises at least one metallic element adjacent to and extending along at least a portion of a perimeter of a loop of the microcoil and enabling a reduction of a strength of the magnetic fields generated by the power source driven microcoil in a direction transverse to said metallic element.