Large-scale digital sky surveys have vastly improved our sensitivity to faint, low-mass, resolved satellite systems in the local universe, pushing us closer to discovering the very threshold of galaxy formation. I will first describe recent efforts to discover ultra-faint dwarf galaxies and star clusters in the Galactic halo with the Dark Energy Camera, with a particular focus on systems discovered in recent years that push the luminosity and surface brightness frontier. I will then describe the discovery and spectroscopic characterization of the growing population of “ultra-faint compact satellites" (UFCSs) of the Milky Way – the least luminous old stellar populations yet identified– and make the case that some of these compact, extremely-low-mass systems that resemble star clusters may actually be the smallest galaxies. Lastly, I will conclude by highlighting individual candidates for the least massive galaxies in the universe (down to stellar masses < 200 Msun) and discuss the implications for the population of ultra-faint systems discoverable by the upcoming Vera C. Rubin Observatory and for galaxy formation physics more broadly.