The　typical　industrial　catalyst　used　for　methanol　synthesis　is　a　multi-component　catalyst　based　on　Cu/ZnO/Al2O3.　The　synergies　between　various　phases　of　this　catalyst　play　a　vital　role　in　defining　the　overall　catalytic　function　and　performance.　To　gain　insights　into　the　role　and　interaction　between　the　relevant　components　and　phases,　ex　situ　and　in　situ　transmission　electron　microscopy　(TEM)　was　deployed　to　investigate　the　structures　and　phases　of　an　industrial　Cu/ZnO/Al2O3　in　its　precursor,　activated　and　reaction　states.　High　structural　inhomogeneity　in　this　material　is　revealed,　i.　e.　the　presence　of　various　phases　with　different　morphologies　and　compositions.　It　is　shown　how　structural　and　compositional　changes　occur　during　hydrogen　treatment　and　how　compositional　inhomogeneity　in　the　starting　material　translates　into　differences　in　the　local　composition　of　the　activated　and　working　catalyst.　The　formation　of　defective　metallic　copper　particles　(stacking　faults　and　twins)　that　are　in　an　intimate　contact　with　zinc　oxide　(poorly　crystalline,　partially　reduced　ZnOx　and　crystalline　ZnO),　alumina,　Zn-Al　oxide　and　carbon-zinc-oxygen　containing　phases　(such　as　zinc　formate)　is　observed.　It　is　also　uncovered　that　alumina　plays　a　potentially　important　role　in　stabilizing　cationic　zinc　species.　This　work　provides　atomic-level　insight　into　the　relevant　state　of　an　industrial　methanol　synthesis　catalyst　and　the　associated　synergistic　interplay　between　the　involved　phases　in　reactive　atmosphere.