Glass is not a crystal. It is amorphous. From the article. Solids are highly organized structures. They include crystals, like sugar and salt, with their millions of atoms lined up in a row, explains Mark Ediger, a chemistry professor at the University of Wisconsin, Madison. "Liquids and glasses don't have that order," he notes. Glasses, though more organized than liquids, do not attain the rigid order of crystals. "Amorphous means it doesn't have that long-range order," Ediger says. With a "solid—if you grab it, it holds its shape," he adds.