Electron microscopy (TEM, SEM, STEM) is often coupled with local elemental analysis (EDX) to reveal local information such as the element distribution . In general, a link can be made between quality of the mixing in the alloy and the emergence of peculiar properties or performance . However, the most classical characterization techniques mentioned above, approach the concept of homogeneity either indirectly (e.g. observing lattice distortion) or with a limited spatial resolution or limited sensitivity (e.g. elemental mapping by STEM-EDX). We argue that, beyond this rough description of "homogeneity", the parameter that truly determines the properties of the alloys is the "atomic level degree of mixing". Thus, it becomes essential to verify and quantify the alloying of the different elements at the atomic scale.