The earliest star formation is believed to occur in small stellar and galactic systems, that subsequently grow into larger galaxies. It was therefore a surprise when we recently found a significant number of massive and evolved galaxies at z>5. Combining HST/ACS, VLT/ISAAC and Spitzer/IRAC data on the GOODS south field, we found 11 massive, i.e. >1011 Mo, galaxies, with ages inferred from population synthesis models in the range 200 Myr to 1 Gyr. The galaxies generally show low levels of on-going star formation and contain no or little dust. The majority of the stars in these galaxies have formation redshift in the range z~9-25. The candidate galaxies are small and compact, with a mean half-light radius corresponding to ~2 kpc. The number density of these galaxies is remarkably high although they contribute very little to the luminosity density at these redshifts. The characteristics of these high-z 'post-starburst' galaxies will be presented as well as the implications, possible precursors and what is needed to detect them with present and future telescopes.