  We review our progress on 3+1D Glasma simulations to describe the earliest
stages of heavy-ion collisions. In our simulations we include nuclei with
finite longitudinal extent and describe the collision process as well as the
evolution of the strongly interacting gluonic fields in the laboratory frame in
3+1 dimensions using the colored particle-in-cell method. This allows us to
compute the 3+1 dimensional Glasma energy-momentum tensor, whose rapidity
dependence can be compared to experimental pion multiplicity data from RHIC. An
improved scheme cures the numerical Cherenkov instability and paves the way for
simulations at higher energies used at LHC.
