This book in honor of Antonio Aurilia provides an overview of one of the most mysterious research fields in theoretical physics, namely the fundamental interactions at energies between the electroweak scale and the Planck scale. The latter includes physics beyond the Standard Model, strings and p-branes, quantum gravity, quantum black holes and early Universe cosmology. A related goal of the work is to present the physical conditions upon which some piece of evidence of new physics at extreme energies can be exposed at current (or near future) experimental facilities. The work is organized in three parts. The first part schematically introduces the problem of fundamental interactions and summarizes the life and work of Prof. Aurilia. The second part forms the body of the book. It contains contributions from internationally recognized specialists who collaborated with Prof. Aurilia, such as R. Balbinot, B. Carr, G. Dvali, A. Fabbri, P. Gaete, J. A. Helayël-Neto, R. Mann, J. Mureika, D. Singleton, A. Smailagic, E. Spallucci and P. Townsend. The third part summarizes the work and draws the conclusions with particular attention to future developments.