11-02U

It is a short essay about statistical physics of complex systems, a direction of studies which nowadays acquires all features of a well defined branch of science with its own subject of analysis, system of notions and methods. The Ising model is chosen as a starting point for an expos\'e. Besides conceptual simplicity such a choice allows to follow formation and development of the phase transitions theory in the Lviv school of statistical physics. Adduced here considerations give a brief account of a talk given at the workshop on the occasion of academician I.R.Yukhnovskii 85th anniversary.