Neutrino physics plays a very important role in understanding several aspects of fundamental physics. In this short review, we revise three different aspects connected to them. Neutrino oscillations at low energy (up to few GeV) offer the possibility to study possible leptonic CP violation whereas at ultra-high energy (E_\nu > 10³ TeV) they could enable to check scenarios of Physics Beyond the Standard Model involving extra-dimensions. On the other hand, e⁺ e^- colliders can help in detecting new heavy Majorana neutrinos suggested by Grand Unified Theories with masses of  O(10² GeV).

PACS numbers: 14.60.Pq, 12.60.--i, 04.50.+h