Taking stock of the quantum Hall effects: Thirty years on

The quantum Hall effects, discovered about thirty years ago have remained one of the most spectacular discoveries in condensed matter physics in the past century. Those discoveries triggered huge expansion in the field of low-dimensional electronic systems, the area grew at an unprecedented rate and continues to expand. Novel and challenging observations, be it theoretical or experimental, have been reported since then on a regular basis. Additionally, the effects have inspired physicists to find analogous situations in far-flung fields as disparate as string theory or black hole physics.