The MOSEL survey is a deep near-IR spectroscopic survey that tracks how galaxies assemble at 1.5<z<3.5. With MOSEL, we confirm a population of Extreme Emission Line Galaxies at z~3 with Oxygen equivalent widths >250 Angstroms and hypothesize that most galaxies at z>3 go through a strong starburst phase. By establishing a benchmark study at z~3, the MOSEL survey contributes to ASTRO-3D, a Centre of Excellence with 250+ members united in understanding the evolution of the matter, light, and elements from the Big Bang to the present day. The Maunakea Spectroscopic Explorer (MSE) builds on revolutionary extragalactic surveys such as MOSEL in ASTRO-3D by providing a high-completeness, magnitude limited sample of galaxy redshifts spanning the epoch of peak cosmic star-formation (z~2). MSE will cover the diverse range of environments probed by surveys such as SDSS and GAMA (groups, pairs, mergers, filaments, voids), but at an epoch when the Universe was under half its current age.