Fundamental properties of neutrinos(\nu ) are studies in nuclei as micro-laboratories. Here nuclear responses for \nu 's are crucial. The present report reviews briefly recent studies of nuclear responses for \nu 's and \nu studies by double beta decays(\beta \beta ) and inverse \beta decays induced by solar and supernova \nu 's. Nuclear responses for charged-current neutrino interactions are mostly given by nuclear isospin--spin responses. They are well studied by charge-exchange reactions with medium energy projectiles. It has been found that ¹⁰⁰Mo has large spin isospin response for \nu 's. Thus ¹⁰⁰Mo isotopes are used as excellent micro-laboratories for spectroscopic studies of \beta \beta decays with a sensitivity on \delimiter "426830A m_\nu \rangle \sim 0.03 eV and realtime studies of low energy solar \nu 's.

PACS numbers: 23.40.--s, 14.60.Pq, 26.65.+t, 95.55.Vj