  Rapid progress is now being made in the study of stellar populations of
galaxies at large lookback times, both in dense clusters and the field.
Dramatic transformations in star formation histories (even morphologies) appear
to prevail among all types of galaxies and in all environments, and these can
be traced to relatively recent times (z ~ 0.2). This article updates to
December 1998 a review made in 1994 to cover the recent watershed of
observational results emerging from the Hubble Deep Field and deep surveys made
with large ground-based telescopes.
