The acceleration of the Universe is one of the biggest puzzles in physics: is it due to a cosmological constant, dynamical dark energy, or modification of gravity? A detailed measurement of growth of structure is required to answer this question. In the first part, I will talk about how galaxy cluster surveys are essential for measuring growth of structure and for constraining cosmic acceleration. I will focus on current and next-generation optical imaging surveys, as well as the synergy with X-ray, submillimeter, and spectroscopic surveys.
In the second part, I will talk about how to probe cosmic star-formation history using cosmic far-infrared background (CIB), which originates from unresolved, dusty star-forming galaxies across cosmic time. Combining tools from intensity mapping surveys and galaxy evolution models, I interpret the CIB measurements from Planck satellite and constrain cosmic star-formation density beyond resolved UV and IR sources.