Over the past decade, redshift surveys and multi-wavelength imaging campaigns have drawn up an empirical picture of how many stars had formed in which types of galaxies over the history of the universe. However, we have yet to unravel the individual pathways along which galaxies evolve, and the physical processes that drive them. Continuing with the previous approach -- larger and deeper photometric samples -- is not adequate to achieve this goal. A change of focus is required.In this ERC project I will embark on a new way to address the question of galaxy evolution. I will do so as Principle Investigator of the recently approved LEGA-C observing program that has been allocated 128 nights of observation time over the next 4 years with ESO's flagship facility the Very Large Telescope. This new survey will produce for 2500 distant (at z~1) galaxies with, for the first time, sufficient resolution and S/N to measure ages and chemical compositions of their stellar populations as well as internal velocity dispersions and dynamical masses. This will provide an entirely new physical description of the galaxy population 7 Gyr ago, with which I will finally be able solve long-standing questions in galaxy formation that were out of reach before: what is the star-formation history of individual galaxies, why and how is star-formation "quenched" in many galaxies, and to what extent do galaxies grow subsequently through merging afterward?LEGA-C is worldwide the largest spectroscopic survey of distant galaxies to date, and ERC funding will be absolutely critical in harvesting this unparallelled database. I am seeking to extend my research group to realize the scientific potential of this substantial investment (6.5M Eur) of observational resources by the European astronomy community. Timing of the execution of the VLT program is perfectly matched with the timeline of this ERC program.