Structural health monitoring (SHM) is a process aimed at providing accurate and in-time information concerning structural health condition and performance. The information obtained from monitoring is generally used to increase the safety, plan and design maintenance activities, verify hypotheses, reduce uncertainty, and to widen the knowledge concerning the structure being monitored. How to realize the effective monitoring is what the researchers devoted to in the past and recent studies. This book, therefore, is focused on the research of critical phenomena in different size-scaled structures, from earth-scale, macro-scale to micro-scale. By analyzing the energy emission from their critical processes, some useful information or suggestion is extracted and to be provided in SHM. Three different forms of energies, acoustic emission (AE), electromagnetic emission (EM) and neutron emission (NE), are selected to be studied in our research. The book is useful for the civil engineers, graduate students, researchers, practitioners, consultants, contractors, infrastructure managers interested in the application of new technologies to structural health monitoring.