Over the past decade, new data have become available from DESY, Jefferson
Lab, Fermilab, and RHIC that connect to parton propagation and hadron
formation. Semi-inclusive DIS on nuclei, the Drell-Yan reaction, and heavy-ion
collisions all bring different kinds of information on parton propagation
within a medium, while the most direct information on hadron formation comes
from the DIS data. Over the next decade one can hope to begin to understand
these data within a unified picture. We briefly survey the most relevant data
and the common elements of the physics picture, then highlight the new
Jefferson Lab data from CLAS, and close with prospects for the future.Comment: 8 pages, 6 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse