Clean　energy　innovation　has　triggered　the　thriving　development　of　electrocatalysts　which　maximize　the　utilization　of　renewable　energy.　Structural　characterization　of　electrocatalysts　is　vital　to　the　rational　design　of　novel　structure,　where　the　fundamentals　of　catalytic　property-structure　relationship　await　exploration.　Among　the　characterization　techniques　for　electrocatalysts,　transmission　electron　microscopy　(TEM)　is　an　essential　tool.　Powered　by　emerging　techniques　such　as　in　situ　TEM,　electron　tomography　and　spectroscopic　imaging,　TEM　has　become　a　“nano-lab”　and　offers　profound　understanding　of　the　electrocatalysts.　In　this　review,　we　briefly　summarize　the　recent　progress　in　TEM　characterization　of　electrocatalysts,　following　three　stages　of　electrocatalysts　from　synthesis,　function　to　deactivation.　Emerging　techniques　are　reviewed　to　address　different　challenges　in　each　stage,　offering　solutions　for　structural　characterization　for　different　needs.　Perspectives　of　TEM　for　electrocatalysts　are　finally　discussed.　©　2024　The　Royal　Society　of　Chemistry.