Glasses have a liquid-like disordered structure but solid-like mechanical properties. This leads to one of the central mysteries of glasses: Why don't they flow like liquids? This question is so important that it was selected by the journal Science in 2005 as one of 125 key, unanswered scientific questions, and one of 11 unsolved important physical issues.
source https://phys.org/news/2021-01-glassy-materials.html