Bits of 10 nm in diameter are written in polyimide Langmuir-Blodgett (LB) films using the atomic force microscope (AFM) combined with scanning tunneling microscope (STM) for simultaneous operation (AFM/STM). Clear spots are observed in the current image at the points where voltage pulses are applied, while no specific feature such as protrusions or holes is observed in the AFM image. These results show that the bit cannot be attributed to metal deposition onto the sample surface or destruction of the LB film, but to the change in conductance of the LB film. The transition speed is faster than 10 mu s, and reproducibility of the bit formation is so high that 10(3) bits, at least, can be formed without tip degradation. These facts show that the combination of LB film and AFM or STM I is useful for storage devices with huge capacity.