Abstract
A review of faint galaxy counts and redshift surveys points to a scientific opportunity for the Gran Telecopio Canarias (GTC) to answer a basic question about galaxy formation: How and when did mass assemble? We argue that the key to answering this question is by focusing on the ``faint-end'' of the galaxy luminosity function out to at least z = 2. This can be exploited with a concerted effort starting with deep counts in the optical and near infrared, followed with near-infrared multiobject spectroscopy, and completed with integral field spectroscopy employing adaptive optics.
