With close to 2000 detected planets, it is striking that we still do not understand how planets form. Their building blocks form in gas disks around young stars, where colliding dust grains form ever-larger aggregates. But this growth is not without limits: larger particles quickly drift towards the star and collide at speeds that shatter them to pieces, long before gravity can bind them together. The mechanisms involved in the assembly and transport of these building blocks remain some of the biggest mysteries of planet formation.Solids in protoplanetary disks evolve differently than the gas, but not independent of it. Observations allow us to directly probe particle growth – the first stage of planet formation. But the gas-solids coupling also enables us to probe the gas disk structure indirectly – just like we cannot see the wind, but we see leaves being moved by it.With this proposal I want to answer some of the key questions of planet formation: (1) What mechanisms drive disk evolution? (2) What role do solids play in the transport of volatiles and the pre-biotic building blocks of life? We will for the first time couple detailed models of the evolution of solids in protoplanetary disks with chemical models on the one side and with hydrodynamical simulations on the other. We aim to derive the unique observable fingerprints of these processes and link those predictions to upcoming observations.With the advent of the ALMA observatory, the prospects of finding these fingerprints are excellent. ALMA will allow us to test our predictions through a wide range of observables at unprecedented sensitivity and resolution, including dust continuum emission, chemical abundance patterns, and isotopic ratios in disks, comets, and our solar system.With our work designed to interpret these observations, we will set the stage for a future understanding of protoplanetary disks and planet formation.