Chromo-Weibel instabilities play a crucial role in the non-equilibrium dynamics of a weakly coupled Quark-Gluon Plasma. In particular, it has been proposed that this collective phenomenon may be the mechanism behind the fast thermalization of the plasma in ultra-relativistic heavy ion collisions. In this context, I will discuss recent advances in the understanding of the exponential growth and isotropization of soft unstable chromo-magnetic fields at short times which are produced by the Chromo-Weibel instabilities. The necessary momentum-space anisotropy that drives the instabilities is produced by the color-glass-condensate initial state. Using the discretized hard loop framework we simulate the 3D+3V realtime evolution of the soft gluonic fields in a longitudinally free streaming expanding background.