  ALMA is a privileged instrument to tackle high redshift galaxies, due to the
negative K-correction in the millimeter domain. Many dusty star-forming
galaxies, invisible in the optical or NIR, will be detected easily through the
peak of their emission in the FIR redshifted in the submm between z=10 and z=5.
Their mass and dynamics will be determined through the CO lines, together with
the efficiency of star formation. Normal intervening galaxies at all z will be
studied through absorption lines in front of quasars, exploring the dense tail
of the column density spectrum. CMB anisotropies could be detected at the
arcsecond scale, the secondary effects (SZ, Vishniak-Ostriker) could test the
re-ionization and the nature of dark energy. The detection of the SZ effect on
a few arcsec scales will allow to map in detail clusters and proto-clusters.
