Professor Simon is well known for his work on minimal surfaces. For a period of 30-35 years very little development occurred in the theory of minimal surfaces; it was generally considered that the outstanding problems were too difficult to be dealt with by existing mathematical theories. During the 1960's, a new mathematical theory - called geometric measure theory - was introduced and developed by Fleming and Federer and it showed promise as a new tool for dealing with minimal surfaces. During the 1970's, ways were found by Simon, Almgren and others for applying the new geometric measure theory to minimal surfaces and many new results were obtained. Professor Simon has emerged as a world authority on minimal surfaces.