A focused ion beam device is described comprising a gas field ion source with an analyzer for analyzing and classifying the structure of a specimen, a controller for controlling and/or modifying the structure of the specimen according to the analysis of the analyzer, an emitter tip, the emitter tip has a base tip comprising a first material and a supertip comprising a material different from the first material, wherein the supertip is a single atom tip and the base tip is a single crystal base tip. Furthermore, the focused ion beam device has a probe current control and a sample charge control. A method of operating a focused ion beam device is provided comprising applying a voltage between a single emission centre of the supertip and an electrode, supplying gas to the emitter tip, analyzing and classifying the structure of a specimen, and controlling the structure of the specimen.