  I discuss our current understanding of the nature of high-redshift (z > 2)
(sub)-millimetre-selected galaxies, with a particular focus on whether their
properties are representative of, or dramatically different from those
displayed by the general star-forming galaxy population at these epochs. As a
specific case study, I present some new results on the one sub-millimetre
galaxy which happens to lie within the Hubble Ultra Deep Field and thus
benefits from the very best available ultra-deep optical-infrared Hubble Space
Telescope and Spitzer Space Telescope imaging. I then consider what these and
other recent results from optical-infrared studies of sub-millimetre and
millimetre selected galaxies imply about their typical masses, sizes and
specific star-formation rates, and how these compare with those of other
star-forming galaxies selected at similar redshifts. I conclude with a brief
discussion of the continued importance and promise of SCUBA2 in the era of
Herschel.
