Although rare in the nearby Universe, gas-rich galaxies with extraordinary star-formation rates (100-1000x the Milky Way at >100 Msun/year) represent the typical massive galaxy in the early Universe ~10 billion years ago. These galaxies’ high star-formation rates are predominantly obscured by dust which re-radiates >95% of the energy from young stars in the (sub)millimeter/far-infrared, hence they are often called dusty star-forming galaxies (DSFGs). Thanks to facilities like the Herschel Space Observatory in the early 2010s, we have successfully mapped the contribution of such DSFGs to cosmic star-formation from z~0 back to z~2, where it appears they are factors of 1000x more common than they are locally and, indeed, dominate. I will discuss current efforts (largely underway with ALMA) to take an unbiased census of completely obscured galaxies from z~2 towards the Epoch of Reionization. The detection of incredibly dust-rich systems (>10^9 Msun of dust) at these early epochs are key to understanding both the early formation mechanisms of dust (from supernovae, AGB stars and via grain growth in the ISM) and the assembly history of the Universe’s most massive galaxies.
