HGMs have become a major field of scientific exploration for the materials, mechanics and physics communities in the coming years. The HGM strategy is not only capable of producing structural materials with unprecedented mechanical properties, but is also effective for developing multifunctional materials. Innovative top-down or bottom-up approaches and material architectures, some of which may be bio-inspired, need to be explored and developed to produce HGMs with superior or disruptive properties. Many fundamental issues still need to be studied by experimentation, analytical modelling, and numerical simulations. Particularly, interface engineering and key interface-related phenomena, such as dispersive strain bands, interactions between geometrically necessary dislocations and zone boundaries, as well as the emergence and evolution of internal stresses, need to be addressed. This symposium, and the future biannual symposia to follow, will be a forum for bringing together a diverse group of multidisciplinary researchers to exchange ideas, discuss key issues, and promote industrial technology development for commercial production and applications.