Due to matter effects, MeV and GeV neutrinos traversing the Earth interior experience significant modifications in flavor mixing that are sensitive to the Earth density profile. For higher energies (tens of TeV), the interaction probability increases enough as to attenuate an incident neutrino flux, providing a different means to study the Earth interior. Therefore, neutrinos allow to study the Earth interior by means of the weak interaction in two widely different ways. In the talk I'll review the state-of-the-art of the Earth Tomography topic, its motivations, existing knowledge, and the prospects of next-generation neutrino telescopes, focusing on Hyper-Kamiokande, to do a tomography of the Earth.