The buildup processes of a [100]-oriented tungsten surface in two steps have been studied by field-electron microscopy (FEM). An initial thermal field treatment is necessary to obtain an ideal tip profile around the [100] orientation. Based on this pretreated tip, some fine and unusual emission patterns result. Three types of buildup processes that cannot be obtained by conventional methods are observed. The experiment shows that the application of FEM can go one step further for the thermal-field case based on conventional methods. (C) 2004 American Vacuum Society.