  Radio wavelengths offer the unique possibility of tracing the total
star-formation rate in galaxies, both obscured and unobscured. As such, they
may provide the most robust measurement of the star-formation history of the
Universe. In this chapter we highlight the constraints that the SKA can place
on the evolution of the star-formation history of the Universe, the survey area
required to overcome sample variance, the spatial resolution requirements,
along with the multi-wavelength ancillary data that will play a major role in
maximising the scientific promise of the SKA. The required combination of depth
and resolution means that a survey to trace the star formation in the Universe
should be carried out with a facility that has a resolution of at least
~0.5arcsec, with high sensitivity at < 1 GHz. We also suggest a strategy that
will enable new parameter space to be explored as the SKA expands over the
coming decade.
