We start with a few concise definitions of the most important concepts discussed in this entry.
Glass transition For molecular liquids, the glass transition denotes a crossover from a
viscous liquid to an amorphous solid. Experimentally, the crossover takes place at the glass
temperature, Tg, conventionally defined as the temperature where the liquid's viscosity
reaches the arbitrary value of 1012 Pa. s. The glass transition more generally applies to
many different condensed matter systems where a crossover or, less frequently, a true …

We briefly review the field of the glass transition, glassy dynamics and aging from a
statistical mechanics perspective. We give a broad introduction to the subject and then
explain the main phenomenology and puzzles encountered in glassy systems. We discuss
the important role played by computer simulations to understand the dynamics of systems
close to the glass transition at the molecular level. We discuss more particularly the idea of a
spatially heterogeneous dynamics that characterizes the relaxation of supercooled liquids …