HAADF-STEM studies have provided detailed morphological insight regarding MoS2, WS2, Co-Mo-S, Ni-Mo-S and Ni-W-S nanostructures in graphite-supported catalysts. It is found that the technique allows the catalytically active edges to be imaged even for single layer metal sulfide structures. Unpromoted MoS2 and WS2 are predominantly present as slightly truncated triangular clusters containing only a single S-M-S layer (M = Mo, W). The addition of promoter atoms results in more heavy truncations consistent with the expected tendency for the Co-Mo-S structures to expose promoted ((1) over bar 010) S-type edges at the expense of unpromoted (10 (1) over bar0) Mo-type edges. However, the HAADF-STEM (High-Angle Annular Dark-field Scanning Transmission Electron Microscopy) results show for the first time that Co-Mo-S and Ni-W-S may also expose. extended high index (11 (2) over bar0) truncations. (c) 2007 Elsevier B.V. All rights reserved.