The accuracy of mapping and quantification in EELS measurements vary with the selection of energy windows, including the background window and signal integration window. On the other hand, the window selections are also affected by the accuracy of energy calibration. For instance, it is very common that an inaccuracy of ~5% or more to the final atomic ratios can be induced by the variation of the energy windows due to the chemical shifts of edges or the very delayed maxima of the edges. Therefore, for each particular EELS system and microscope setting, the use of different energy windows should be investigated in order to find the optimized energy windows to obtain the most consistent results.