All Creatures Great and Small: Probing the Evolution and Structure of Mass from Sub-Galactic to Supercluster Scales using Gravitational Lensing

Understanding the distribution of mass on cosmic scales provides context for a number of astrophysical topics, including galaxy evolution, structure formation, and cosmology. In this dissertation, I present new research into the distribution of mass throughout the universe, ranging from small (sub-galactic) to large (Supercluster) scales. This work is spread over four separate studies, each focusing on slightly different cosmological distance scales.;In the first study, I employ strong and weak gravitational lensing to measure the mass profiles of a sample of massive elliptical galaxies at moderate redshift (z ∼ 0.6). I find that the total mass profile is best described by an isothermal (r -2) distribution, which disagrees with predictions made by numerical simulations. This disagreement provides important clues about the poorly understood interactions between dark matter and baryons. Furthermore, I compare these results to those of a low-redshift (z ∼ 0.2) galaxy sample, and this allows me to constrain the evolution of galaxy-scale mass profiles over a timescale of ∼ 7 billion years.;In the second and third studies, I combine strong lensing constraints and high-resolution adaptive optics imaging to develop new mass models for the lens systems B0128+437 and B1938+666. I use these models to search for the presence of small-scale substructures (satellite galaxies) in the vicinity of the host lens. While structure formation models predict a large number of substructure galaxies orbiting a host, this does not agree with observations of the local universe, where only a handful of satellites are seen. I compare the upper-limit substructure constraints from the two strong lenses to the properties of known Milky Way satellites, and lay the foundation for a comprehensive census of extragalactic substructure, using a large sample of lenses to better resolve the tension between theory and observation.;Finally, in the fourth study, I focus on mass at super-galactic scales, utilizing weak lensing to probe the structure of the high-redshift ( z ∼ 0.9) supercluster Cl 1604. Using deep Hubble Space Telescope imaging, I create the first ever two-dimensional mass map of the full supercluster field, and measure the virial masses of the three largest individual clusters. With this measurement, I constrain the mass environments of bound systems at earlier cosmological epochs, and provide complementary information to an already rich data set.