ИСТИНА

I review observational results focused on the solar–stellar connections, which help us to trace changes in physical conditions on the Sun at different stages of its life. Estimate of stellar ages from the period of the axial rotation (the method of the gyrochronology) permits us to study dependence of the activity on the age. The quasi-stationary X-Ray-and FUV-radiation of the outer atmosphere of the young Sunis estimated. Both most powerful non-stationary phenomena and quasi-stationary activity are discussed on the base of space missions and ground-based observations. Joint analysis of superflares and stellar magnetic fields on solar-type stars gives a chanceto estimate the maximal possible energy of stellar flares; that allows us to understand the origin of extreme events on the Sun.