The high-precision data from LEP and the other experimental results from high-energy laboratories the world over have given with unprecedented accuracy a picture-perfect agreement between theory and experiment. The problem of present-day physics is how to reconcile the successes of the Standard Model with the compelling reasons for the existence of new physics beyond it. In fact there is no question that the ultimate theory is superstring: the Standard Model being an intermediate step toward the Theory of Everything.The theoretical and phenomenological aspects of those problems are reviewed and discussed in this volume, together with the most recent experimental data.