  The history of galaxy formation via star formation and stellar mass assembly
rates is now known with some certainty, yet the connection between high
redshift and low redshift galaxy populations is not yet clear. By identifying
and studying individual massive galaxies at high-redshifts, z > 1.5, we can
possibly uncover the physical effects driving galaxy formation. Using the
structures of high-z galaxies, as imaged with the Hubble Space Telescope, we
argue that it is now possible to directly study the progenitors of ellipticals
and disks. We also briefly describe early results that suggest many massive
galaxies are forming at z > 2 through major mergers.
