Analysis of information sources in references of the Wikipedia article "List of unsolved problems in physics" in English language version.
The deepest and most interesting unsolved problem in solid state theory is probably the theory of the nature of glass and the glass transition.
The deepest and most interesting unsolved problem in solid state theory is probably the theory of the nature of glass and the glass transition.
The deepest and most interesting unsolved problem in solid state theory is probably the theory of the nature of glass and the glass transition.