The universe we observe today is dotted with galaxy clusters separated by vast voids, in sharp contrast to its initial state, which was nearly uniform with only minor density fluctuations. The evolution from this early uniformity to today's complex structure of galaxies is a profound transformation, with many intermediate processes still unexplained. In this talk, I will explore this transformation, focusing on the reconstruction of the initial density and displacement fields of galaxies observed through spectroscopic surveys. I will present the latest cosmological measurements from the DESI data and discuss advancements in reconstruction algorithms that have enabled significant improvements across several areas, including peculiar velocity analysis and the kinematic Sunyaev-Zel’dovich (kSZ) effect.