The use of a combined focused ion beam/environmental scanning electron microscope (FIB/ESEM) offers new possibilities for imaging the internal structure of complex heterogeneous polymeric samples. The use of the focused ion beam, using positively charged gallium ions in conjunction with a measured 'defocused' low-energy primary electron beam, has permitted milling through the heterostructure to be achieved in a controlled way, exposing the inner structure, without introducing significant ion beam damage/destruction into the sample. The subsequent use of the environmental scanning electron microscope for imaging the revealed internal structure has then enabled insulating polymer structures to be imaged, without charging problems. Cross-sections of a 900-nm-thick spun cast film of phase-separated polystyrene-polybutadiene blends have been successfully milled and imaged; the morphology agreeing with previous results produced using ultramicrotomy and transmission electron microscopy.