  I describe an observational program aimed at understanding the radio emission
from distant, rapidly evolving galaxy populations. These observations were
carried out at 1.4 and 8.5 GHz with the VLA centered on the Hubble Deep Field.
Further MERLIN observations of the HDF region at 1.4 GHz provided an angular
resolution of 0.2" and when combined with the VLA data produced an image with
an unprecedented rms noise of 4 $\mu$Jy. All radio sources detected in the VLA
complete sample are resolved with a median angular size of 1-2". The
differential count of the radio sources is marginally sub-Euclidean ($\gamma$ =
-2.4 $\pm$ 0.1) and fluctuation analysis suggests nearly 60 sources per
arcmin$^2$ are present at the 1 $\mu$Jy level. A correlation analysis indicates
spatial clustering among the 371 radio sources on angular scales of 1- 40
arcmin.
  Optical identifications are made primarily with bright (I = 22) disk systems
composed of irregulars, peculiars, interacting/merging galaxies, and a few
isolated field spirals. Available redshifts span the range 0.2 - 3. These clues
coupled with the steep spectral index of the 1.4 GHz selected sample are
indicative of diffuse synchrotron radiation in distant galactic disks. Thus the
evolution in the microjansky radio population is driven principally by
star-formation.
  I have isolated a number of optically faint radio sources (about 25% of the
overall sample) which remain unidentified to I = 26-28 in the HDF and flanking
optical fields. Several of these objects have extremely red counterparts and
constitute a new class of radio sources which are candidate high-z dusty
protogalaxies.
