The impressive development of focused ion beam (FIB) systems from the laboratory level to high performance industrial machines during the last twenty years is briefly reported. The design and the functional principle of a liquid metal ion source as well as a FIB column are described. The main application fields of the FIB technology are discussed. More in detail the Rossendorf FIB activities, like writing Co+ implantation in silicon to fabricate CoSi2 microstructures by ion beam synthesis and the writing Ga+ FIB implantation to create a patterned etch stop during a following anisotropic etching for micromechanical 3D structure fabrication are presented.