  According to the Random First Order Transition (RFOT) theory of glasses, the
barriers for activated dynamics in supercooled liquids vanish as the
temperature of a viscous liquid approaches the dynamical transition temperature
from below. This occurs due to a decrease of the surface tension between local
meta-stable molecular arrangements much like at a spinodal. The dynamical
transition thus represents a crossover from the low $T$ activated bevavior to a
collisional transport regime at high $T$. This barrier softening explains the
deviation of the relaxation times, as a function of temperature, from the
simple $\log \tau \propto 1/s_c$ dependence at the high viscosity to a
mode-mode coupling dominated result at lower viscosity. By calculating the
barrier softening effects, the RFOT theory provides a {\em unified} microscopic
way to interpret structural relaxation data for many distinct classes of
structural glass formers over the measured temperature range. The theory also
provides an unambiguous procedure to determine the size of dynamically
cooperative regions in the presence of barrier renormalization effects using
the experimental temperature dependence of the relaxation times and the
configurational entropy data. We use the RFOT theory framework to discuss data
for tri-naphthyl benzene, salol, propanol and silica as representative systems.
