Galaxy surveys of the next decade will observe hundreds of millions of galaxies over unprecedented cosmic volumes. They will produce detailed 3D maps of the Universe that we can use to precisely measure the growth and expansion histories of the Universe. They will also observe photometry and spectroscopy of each galaxy that encode its physical properties. In my talk, I will present how we will extract this cosmological information from the major galaxy surveys that I am leading: the Dark Energy Spectroscopic Instrument (DESI) and the Prime Focus Spectrograph (PFS). Furthermore, I will demonstrate how my work, ranging from survey design to the cutting-edge machine learning methods I have pioneered, will maximize the scientific impact of these surveys. In particular, I will show how I will test the standard "Lambda-CDM" cosmological model in new regimes and with unmatched precision to probe the nature of dark energy. I will also show how I will extract detailed galaxy properties, such as star formation or chemical enrichment histories, of millions of galaxies across 12 billion years of cosmic history to constrain the physical processes that drive galaxy evolution.
