What is the Standard Model of Elementary Particles and Why We Have to   Modify It
  We introduce the standard model of elementary particles and discuss the reasons why we have to modify it. Emphasis is put on the indications from the neutrinos and on the role of the Higgs particle; some promising theoretical ideas, like quark-lepton symmetry, existence of super-heavy ``right-handed'' neutrinos, grand unification and supersymmetry at the weak scale, are introduced and shortly discussed. 
Francesco Vissani (Gran Sasso)