The glass transition: How do complex craggy free energy landscapes emerge?

Glass as a material was already known in ancient Egypt. Now its use for windows, bottles, etc. is very common; thus, it may sound surprising that the glassy state of matter and the transition from an undercooled melt to this state are grand challenge problems of physics. This article describes the basic concepts; then it points out how the discovery of “spin glasses” and the theory by Giorgio Parisi has given a new boost to the interest in these problems. The status of a theory of the glass transition will be critically discussed.