  The Hubble space telescope observations of the northern Hubble deep field,
and more recently its counterpart in the south, provide detections and
photometry for stars and field galaxies to the faintest levels currently
achievable, reaching magnitudes V ~ 30. Since 1995, the northern Hubble deep
field has been the focus of deep surveys at nearly all wavelengths. These
observations have revealed many properties of high redshift galaxies, and have
contributed important data on the stellar mass function in the Galactic halo.
