A microscopic metallic structure is produced by creating or exposing a patterned region of increased conductivity and then forming a conductor on the region using electrodeposition. In some embodiments, a microscopic metallic structure is formed on a substrate, and then the substrate is etched to remove the structure from the substrate. In some embodiments, a focused beam of gallium ion without a deposition precursor gas scans a pattern on a silicon substrate, to produce a conductive pattern on which a copper structure is then formed by electrochemical deposition of one or more metals. The structure can be freed from the substrate by etching, or can used in place. A beam can be used to access an active layer of a transistor, and then a conductor can be electrodeposited to provide a lead for sensing or modifying the transistor operation while it is functioning.