  We discuss the transverse momentum broadening of hard probes traversing an
evolving glasma, which is the earliest phase of the matter produced in
relativistic heavy-ion collisions. The coefficient $\hat q$ is calculated using
the Fokker-Planck equation, and an expansion in the proper time $\tau$ which is
applied to describe the temporal evolution of the glasma. The correlators of
the chromodynamic fields that determine the Fokker-Planck collision term, which
in turn provides $\hat q$, are computed to fifth order in $\tau$. The momentum
broadening is shown to rapidly grow in time and reach a magnitude of several
${\rm GeV^2/fm}$. We show that the transient pre-equilibrium phase provides a
contribution to the energy loss of hard probes which is comparable to that of
the long lasting, hydrodynamically evolving, equilibrium phase.
