Spin is a fundamental quantum number carried by elementary particles and playing important roles in fundamental physics. We show two examples where spin is used to extract symmetry violations in the nature. We are investigating the origin of the proton spin in polarized proton-proton collisions at RHIC. The polarized proton is utilized to extract parity violating asymmetry originated in W production. Such reaction is sensitive to the spin flavor structure of the sea quarks in the proton. We discuss the current status and prospects of the W physics at RHIC. Another example is the measurement of the anomalous magnetic moment (g-2) and electric dipole moment (EDM) of muon at J-PARC. An EDM is parity-odd and time-reversal-odd object and it would imply CP violation in the lepton sector, if non-zero value is discovered. We discuss the experiment to measure g-2 and EDM at the same time with novel technique: ultra-cold muon beam and ultra-precision magnet.