Perhaps as important as the work for which he won the Nobel prize is his invention of modulation doping, a method for making extremely high mobility two dimensional electron systems in semiconductors. This enabled the later observation of the fractional quantum Hall effect, which was discovered by Störmer and Tsui in October 1981 in an experiment carried out in the Francis Bitter High Magnetic Field Lab at the Massachusetts Institute of Technology. Within a year of the experimental discovery, Robert Laughlin was able to explain its results. Störmer, Tsui and Laughlin were jointly awarded the 1998 Nobel Prize in Physics for their work.