Since grain boundaries come with an energetic penalty compared to the crystalline state, nanostructured materials have a high driving force for coarsening and are typically unstable when heated. A solution to this problem is the planned doping of these materials with segregating elements that reduce grain boundary energy. In this talk, we extend this concept to amorphous complexions, which are phase-like features that have lower energy than the clean boundaries at high temperature where entropic effects can dominate. We present materials selection rules for a wide variety of transition metals, providing guidelines to promote the formation of amorphous intergranular films. After testing these rules in binary Cu-based alloys, we extend our study to ternary systems and other materials, such as Ni- and Fe-based alloys. As a whole, we find that nanostructured metals decorated with amorphous intergranular films can be survive at temperatures >90% of their melting temperature for multiple days.