This time we showcase a very interesting paper that highlights once more the need for extremely stable imaging conditions when performing in situ heating. In this contribution, the authors have imaged octahedral faceted nanoparticles at different temperatures. These particles are highly attractive fuel cell catalysts as a result of their activity for the oxygen reduction reaction (ORR). However, their surface compositional and morphological stability currently limits their long-term performance in real membrane electrode assemblies (MEAs). Specifically, they authors have performed in situ heating of compositionally segregated PtNi1.5 octahedral nanoparticles inside a transmission electron microscope, in order to study their compositional and morphological changes.