A typical EELS spectrum acquired with 100 kV electrons through a MgO nanocube. It extends over 1500 eV and exhibits three major contributions : (i) in blue above typically 50 eV, the core energy-loss domain made of a regularly decaying background on which are superposed characteristic edges O-K and Mg-K; (ii) in green, from about 1 or 2 eV up to 50 eV, the low energy-loss domain which contains most of the intensity in an EELS spectrum; (iii), in red, the zero-loss peak now encompassing the ultra-low energy-loss domain which has only been explored with the latest generation of STEM instruments incorporating a monochromator. See text for discussion.