Structural damage in materials is a “top priority” to be investigated by material scientists all over the world. The future or limit of a material to be used in structural applications depends upon it, as safety and environmental protection are important issues in national policies. The acoustic emission (AE) technique offers the possibility to listen to the damage process when and where it occurs. This paper focuses on a number of cases investigated at the department MTM using AE to analyze damage in various application fields. The tools handled to interpret the AE signals, the relation between AE and the residual properties and the additional understanding of a particular material behavior will be outlined. The fatigue damage of CFRP, the curing of concrete and the corrosion of carbon steel and stainless steel will be discussed as case studies.