  We have carried out a thorough optical study of the closest star formation
jet. The inner arcminute surrounding the class 0/I binary protostar L1551 IRS5
and its associated jet (HH154) have been observed using the Hubble Space
Telescope with the WFPC2 camera, the ESO New Technology Telescope with the EMMI
spectrograph and the Nordic Optical Telescope with the ALFOSC spectrograph.
This data set is compared to earlier ground based imaging with the aim to study
the evolution of this particular jet, and its possible interaction with the
molecular material in the bipolar molecular outflow associated with this
source. The velocity field of the jet is mapped out. The highest velocities are
found in the vicinity of the recently discovered X-ray source emanating from a
shock in this jet. The energy radiated by the X-ray source is compatible with
these velocities. The \halpha and \hbeta emission from the jet is used to
determine the extinction, which is found to increase inwards in the jet towards
the protostar. The extinction towards the X-ray source is consistent with the
one determined from the X-ray spectrum.
