Several theoretical proposals had been made to explain the fractional quantum Hall effect, most notably by Laughlin. However, the status of our theoretical understanding seemed quite unsatisfactory to me. In 1989, when I was a post-doctoral research associate, it suddenly occurred to me that I could unify the fractional quantum Hall effect with the well-understood phenomenon of "integral quantum Hall effect," discovered in 1980 by von Klitzing.

This unification led me to postulate the formation of a new class of fermions in this system which I named "composite fermions." The fractional quantum Hall effect is now understood in terms of composite fermions. There has been extensive work toward measuring various properties of composite fermions—for example, their mass, statistics, magnetic moment, etc.—and many other states of composite fermions have been observed, such as their Fermi sea or their paired state.

No practical applications yet. There is an intriguing proposal for building quantum computers based on the composite fermion physics, however. In certain conditions composite fermions pair up, much like electrons in superconductors. The excitations of this state are believed to be neither bosons nor fermions but what are known as anyons. Some scientists believe that their "topological" properties can be used for quantum computation. It is too soon to tell how this will develop.

We now have a completely new way of understanding the fractional quantum Hall effect, which provides a new paradigm for collective behavior in nature, much in the same way as superfluidity and superconductivity. Many exciting discoveries are being made in this field and many problems remain open. Aside from the potential for quantum computation, an exciting prospect would be the future discovery of fractional quantum Hall-like structures in other systems, such as rapidly rotating Bose-Einstein condensates, or in graphene (a single layer of graphite).