Gerardus ‘t Hooft held his Nobel Lecture on 8 December 1999, at Aula Magna, Stockholm University.

Summary: The theoretical problem of small distance structures of particles and fields is illustrated by the differences between observed and bare mass and charge. The concept of renormalization is introduced. ‘t Hooft explains spontaneous symmetry breaking and the role of the Higgs particle, one missing part of the standard model for particles. The energy dependence of the different interaction coupling strengths leads to super symmetry and the experimental search at CERN. The lecture ends with a brief discussion of string theories.