  A study of energy behavior of the pion spectra and interferometry scales is
carried out for the top SPS, RHIC and LHC energies within the hydrokinetic
approach. The latter allows one to describe evolution of quark-gluon and hadron
matter as well as continuous particle emission from the fluid in agreement with
the underlying kinetic equations. The main mechanisms that lead to the
paradoxical, at first sight, behavior of the interferometry scales, are
exposed. In particular, a slow decrease and apparent saturation of
$R_{out}/R_{side}$ ratio with an energy growth happens due to a strengthening
of positive correlations between space and time positions of pions emitted at
the radial periphery of the system. Such en effect is a consequence of a
developing of the pre-thermal collective transverse flows and an increase of
the initial energy density in the fireball.
