Recent results of source function imaging from AGS through CERN SPS to RHIC

Recent femtoscopic measurements involving the use of an imaging technique and a newly developed moment analysis are presented and discussed. We show that this new paradigm allows robust investigation of reaction dynamics for which the sound speed c_s ≠ 0 during an extended hadronization period. Source functions extracted for charged pions produced in Au+Au and Pb+Pb collisions show non-Gaussian tails for a broad, selection of collision energies. The ratio of the RMS radii of these source functions in the out and side directions are found to be greater than 1, suggesting a finite emission time for pions.