4HS will obtain spectra and redshifts for ~6 million galaxies with high and unbiased completeness across the full southern hemisphere, to define the benchmark reference sample of galaxies at \(z < 0.15\). The result is a dataset with exceptional legacy value with wide applicability. As examples: 4HS will provide the \(z\sim0\) anchor for evolutionary studies with WAVES; the critical field sample for cluster surveys like CHANCES; and the mass-limited comparison sample for HI or X-ray selected samples from WALLABY or eROSITA. In combination with other flagship surveys including VRO-LSST, VHS, WISE, Euclid, ASKAP/MeerKAT/SKA, 4HS will establish a transformative laboratory for studying the baryon cycle within and around galaxies as a function of galaxy/halo mass, as well as local/large-scale environment. At the same time, 4HS cosmology will measure the cosmic velocity field over ~1 Gpc from the peculiar velocities of ~500,000 massive early type galaxies. By mapping mass and motion on the largest possible scales, 4HS will reveal a complete picture of gravitational collapse and cosmic structure formation in the Local Volume.