  Next generation CMB experiments with arcmin resolution will, for free, lay
the foundations for a real breakthrough on the study of the early evolution of
galaxies and galaxy clusters, thanks to the detection of large samples of
strongly gravitationally lensed galaxies and of proto-clusters of dusty
galaxies up to high redshifts. This has an enormous legacy value. High
resolution follow-up of strongly lensed galaxies will allow the direct
investigation of their structure and kinematics up to z~6, providing direct
information on physical processes driving their evolution. Follow-up of
proto-clusters will allow an observational validation of the formation history
of the most massive dark matter halos up to z~4, well beyond the redshift range
accessible via X-ray or SZ measurements. These experiments will also allow a
giant leap forward in the determination of polarization properties of
extragalactic sources, and will provide a complete census of cold dust
available for star formation in the local universe.
