"Neutrino masses and mixing are the most tangible evidence for the shortcomings of the Standard Model and finding a more complete theory remains the most challenging task for elementary particle physics. Neutrinos can lead us on the trail to new physics, together with experiments at the LHC, flavor physics and cosmology. The best time for carrying out this project is now. Neutrino physics is more vibrant than ever as a renewed flow of key data has just begun. First evidence that the hitherto unknown value of the third neutrino mixing angle theta(13) is sizeable raises concrete hopes of observing CP-violation in the lepton sector, triggering new ideas for model building. Moreover, the entire neutrino community is intrigued by several experimental anomalies that hint at unexpected neutrino properties. This animated scenery provides an ideal stage for the ""NuTrails"" project, having neutrinos as its main actors. Following the trails of these elusive particles to the smallest scales will serve as a formidable guide to new discoveries.More specifically, this project will focus on two different classes of standard-model extensions. First, signs for new physics originating from heavy mediators at the TeV scale will be studied. Second, manifestations of a new low-energy scale will be sought, hunting for light ""sterile"" neutrinos with mass in the eV range. Theoretical questions related to neutrino flavor conversion in the presence of such new properties will be addressed. Furthermore, observable consequences for present and future experiments will be quantified. These results will have far-reaching implications, extending from particle phenomenology to astrophysics and cosmology. Most importantly, the quantitative simulations will decisively influence the next round of experimental strategies."