Nuclei, which consist of nucleons in good quantum states, are good micro-laboratories for studying fundamental interactions and elementary particles. In particular, nuclear double beta decays and nuclear rare decays are used to study neutrinos (\nu) and symmetries in nuclear microlaboratories. Subjects discussed include (i) \nu-masses and weak interactions studied by nuclear double beta decays (\beta\beta), (ii) neutrino nuclear responses for solar-nu and \beta\beta - \nu, (iii) strange-quark weak processes studied by hyperon weak decays in nuclei, and (iv) nucleon decays studied by nuclear rare deexcitations. All these subjects are associated with neutrinos and symmetries beyond the standard theory.

PACS numbers: 21.10.Tg, 23.40.--s, 27.60.+j, 27.70.+q