"A2C2S is a large survey of 122 normal star-forming galaxies observed in the [CII]-158µm line and continuum. It aims at understanding stars, gas and dust properties at a time of rapid galaxy maturation after the end of HI reionization, at redshifts 4<z<6. With A2C2S it becomes possible to trace the cosmic time evolution of the star formation rate from a complete census at this key epoch, as well as to conduct a detailed characterization of ISM properties using LFIR/LUV and C+/FIR diagnostics. Dynamical masses are estimated from spectrally resolved C+, openning the way to measurements of the gas fraction and its evolution. A2C2S is providing a rich Legacy in the data-rich extragalactic survey fields ECDFS and COSMOS enabling studies with future facilities like JWST or the ELT. The key results will be presented at this meeting."