Atomic nuclei can be used as spatial analyzers of the hadronization process in semi-inclusive deep inelastic scattering. The study of this process using fully-identified final state hadrons began with the HERMES program in the late 1990s, and is now continuing at Jefferson Lab. In the measurement described here, electrons and positive pions were measured from a 5 GeV electron beam incident on targets of liquid deuterium, C, Fe, and Pb using CLAS in Hall B. The broadening of the transverse momentum of positive pions has been studied in detail as a function of multiple kinematic variables, and interpreted in terms of the transport of the struck quark through the nuclear systems. New insights are being obtained into the hadronization process from these studies; and experiments of this type can be relevant for the interpretation of jet quenching and proton-nucleus collisions at RHIC and LHC. These measurements will be extended in the next few years with the approved JLab experiment E12-06-117, and later at a future Electron-Ion Collider. © 2012 American Institute of Physics.