S ince the revolution initiated by Einstein with his formulation of general relativity, the 20^th century has witnessed remarkable developments in our understanding of the gravitational interaction. In particular, emergence of string theory as providing a framework, in which both a microscopic description of gravity and a unification of all fundamental forces might be consistently achieved, is probably one of the main theorical landmarks of the physics of the last fifteen years. Its implications have just begun to be uncovered.

This volume collects the contributions that were discussed at the meeting "Strings and Gravity: Tying the Forces Together", which took place in Brussels from October, 19^th to October, 21^st, 2001. This meeting gathered most of the top experts in this field for active discussions on the state-of-the-art in gravity, gauge and string theory. The contributions range from black holes and cosmological questions (string-inspired cosmological scenarios, dark energy and the fate of our universe, relaxation of the cosmological constant), to exotic low energy physics with large extra dimensions and more theoretical issues in string theory and quantum gravity (gauge/gravity, duality, D-branes, gauge invariance in cosmological spaces, more formal questions related to unitary and symmetry).