Interestingly, the nature of glass is one of the most important open problems in physics. "The deepest and most interesting unsolved problem in solid state the

Interestingly, the nature of glass is one of the most important open problems in physics. "The deepest and most interesting unsolved problem in solid state theory is probably the theory of the nature of glass and the glass transition. This could be the next breakthrough of the coming decade. The solution of the problem of spin glass in the late 1970s had broad implications in unexpected fields like neural networks, computer algorithms, evolution, and computational complexity. The solution of the more important and puzzling glass problem may also have a substantial intellectual spin-off. Whether it will help make better glass is questionable." P. W. Anderson, Princeton, 1995. (In Science, "Through the Glass Lightly.") Still unsolved, but of considerable interest.