The main objective of the proposed COST Action is to gather theoretical and experimental working groups from the relevant communities (with proper geographical, age and gender balance) to work in the prediction and possibility of detection of physical phenomena characteristic from quantum gravity theories. This cooperation is necessary to address this challenge properly, which may result in extraordinary advancements in fundamental physics. A second objective will be the formation of a generation of scientists that will be competent in the interdisciplinary expertise that is needed in the effective search of quantum gravity footprints in the production, propagation and detection of these cosmic messengers. Whatever the outcomes of this search may be, it will certainly have an important impact on science through a better understanding of the Universe and its fundamental laws