Research in theoretical physics of elementary particles and strings will include: Precision calculations of the quantum corrections to the Standard Model of elementary interactions. This kind of calculations has been crucial, already, to show that the Standard Model is the most successful theory of elementary interactions ever. In the present and future, it shall allow us to compare this theory with experiment, with accuracy sufficient to open a window on possible new physics. ii) Non-perturbative calculations in string theory. Strings are the only reliable theory of (perturbative) quantum gravity available today. Some calculations can be performed using to the fullest extent special symmetries (extended supersymmetry, duality etc.). These calculations are crucial in trying to understand the deepest aspect of string theory, as, for instance, to which degree it is unique. They also provide a powerful technique for understanding the physics of strongly interacting quantum fields.