The ion-shadow method, an ion milling process using carbon particles as the mask material, is investigated as a means of preparing resistance random access memory (ReRAM) samples for in situ transmission electron microscopy (TEM). With a milling time of 1 hour (Ar+, 5 kV, 1 mA), multiple long needles (>5 mu m), on which there are miniaturized ReRAM devices comprising a ReRAM insulating layer sandwiched by two metallic electrodes, are formed on the substrate. Device sizes of up to several hundreds of nm are easily obtained with the method. The internal part of small devices (i.e., up to 100 nm) can be observed by TEM. Electrical measurements using an in situ TEM holder demonstrate that sufficient electric contact is obtained without any electric shortage between the electrodes due to re-deposition of milled material. The ion-shadow method is confirmed to be a quick and easy method suitable for in situ TEM experiments, especially for ReRAM devices which are highly susceptible to destruction during the switching operation. (C) 2012 Elsevier B.V. All rights reserved.