Abstract.Precision measurements are an integral part of particle physics. They are essential for determining free parameters of the Standard Model (SM), and also for searching for signals of new physics beyond the SM. Apart from collider results from LEP, Tevatron, and the LHC, the increasing role is being played by precision measurements performed at much lower energies, well below the weak scale. In this talk I will review the place of nuclear beta transitions in this programme. Thanks to the improving accuracy of experiment, theory, and lattice calculations, the precision level of beta transitions is reaching 10^-4 in some cases. In particular, the so-called superallowed beta transitions give currently the most precise determination of the Vud parameter in the CKM matrix. I will describe the wide spectrum of
current and planned experiments, and how they improve our understanding of the SM and non-SM physics. Finally, I will report on an upcoming work of using the so-called mirror beta transitions to constrain new physics beyond the SM.
(The slides will be available here)