  A first attempt has been made to extract the evolution of radial flow from
the analysis of the experimental data on electromagnetic probes experimentally
measured at SPS and RHIC energies. The $p_T$ spectra of photons and dileptons
measured by WA98 and NA60 collaborations respectively at CERN-SPS and the
photon spectra obtained by PHENIX collaboration at BNL-RHIC have been used to
constrain the theoretical models, rendering the outcome of the analysis largely
model independent. We argue that the variation of the radial velocity with
invariant mass is indicative of a phase transition from initially produced
partons to hadrons at SPS and RHIC energies.
