Metals trace the full evolution of the Universe : from primordial Helium and Lithium in the big-bang nucleosynthesis to all heavier elements produced in stars and explosive events. Determining their relative abundances in different environments, and across cosmic time, reveals the underlying star formation history and gas exchange processes. Recent progress in instrumentation and modeling now permits using metal production and distribution to test our ideas of galaxy evolution at many different hierarchical scales : from stellar clusters to clusters of galaxies. The hierarchical build up of present-day structures at different redshifts can also be followed, which go in parallel with the build-up of stellar and metal mass. These processes are interwoven : during most of cosmic history metal production happens at stellar scales, but metal distribution is effective on spatial scales covering several orders of magnitudes. Therefore simulations require exceptional computational power, and tracing metals across cosmic time needs an equivalent investment in observational facilities. Both aspects are reaching some maturity in these days, so we propose a meeting to review the state of the art in all the different research areas. Possible meeting sessions and invited speakers are listed below and above.