Towards Microscopic Theory of Phase Transitions: Correlation Radii and   Critical Indices
  From the microscopic point of view almost all bonds between particles of condensed substances must be performed by exchanges of virtual photons. Consequently the duration of their virtuality must be longer than the extent of their free path in the substance, the magnitudes of all expressions in such inequality are known from low frequencies scattering. This approach allows to suggest that the break of some set of bonds of particles, i.e. the phase transitions, will be originated just at the reversing of established inequality. Such assumption leads to definition of the radius of correlations or bonds: $R_{c}\symbol{126} E^{-2/3}$ that proves the universality of this critical index. The energies E, which can be liberated at phase transitions, are definite for different types of critical phenomena. Reformulation of the Ginzburg-Landau model of phase transitions via expansion of thermodynamic potentials over $R_{c}$, instead temperatures distance, leads to the correct system of all critical indices. 
M.E. Perel'man