Glasses are neither fluids nor crystals. They are amorphous solids and one of the big puzzles in condensed matter physics. For decades,the question of how glass forms has been a matter of controversy. Is it because some regions freeze their thermal motion? Or is it because there are particles or clusters which do not fit to form a crystal? At least for the model system of tough spheres, researchers at Johannes Gutenberg University Mainz (JGU) in Germany possess now taken a major leap in reconciling these two opposing views.
Source: phys.org