  Nuclei are unique analyzers for the early stage of the space-time development
of hadronization. DIS at medium energies is especially suitable for this task
being sensitive to hadronization dynamics, since the production length is
comparable with the nuclear size. This was the driving motivation to propose
measurements at HERMES using nuclear targets, and to provide predictions based
on a pQCD model of hadronization [1]. Now when the first results of the
experiment are released [2,3], one can compare the predictions with the data.
The model successfully describes with no adjustment the nuclear effects for
various energies, zh, pT, and Q2, for different flavors and different nuclei.
It turns out that the main source of nuclear suppression of the hadron
production rate is attenuation of colorless pre-hadrons in the medium. An
alternative model [4] is based upon an ad hoc assumption that the colorless
pre-hadron is produced outside the nucleus. This model has apparent problems
attempting to explain certain features of the results from HERMES. A good
understanding of the hadronization dynamics is important for proper
interpretation of the strong suppression of high-pT hadrons observed in heavy
ion collisions at RHIC. We demonstrate that the production length is even
shorter in this case and keeps contracting with rising pT.
