The cover of Nature (4 May 2017, Volume 545, Number 7652) shows the microstructure of an exceptionally strong thin-film magnesium alloy captured using transmission electron microscopy. Produced by dual-phase nanostructuring, this alloy has a strength that approaches the ideal theoretical limit. Nanostructuring of crystalline metal alloys can yield high-strength materials, but these tend to soften as the strain is increased. In this latest work, IAS Senior Fellow Professor Jian Lu and his team combine the benefits of nanocrystallinity with those of single-phase amorphous metallic glasses to yield a dual-phase material --- MgCu2 nanocrystalline grains (6 nm) enclosed in an amorphous glassy shell (2 nm) --- that resulted in the strongest thin-film magnesium alloy to be made so far. Cover image: Susanna Siu & Ge Wu/City University of Hong Kong.