We have investigated recrystallization of amorphous Yttrium Iron Garnet (YIG) by annealing in oxygen atmosphere. Our findings show that well below the melting temperature the material transforms into a fully epitaxial layer with exceptional quality, both structural and magnetic. In ferromagnetic resonance (FMR) ultra low damping and extremely narrow linewidth can be observed. For a 56?nm thick layer a damping constant of ??=?(6.15?±?1.50)?·?10?5 is found and the linewidth at 9.6?GHz is as small as 1.30?±?0.05?Oe which are the lowest values for PLD grown thin films reported so far. Even for a 20?nm thick layer a damping constant of ??=?(7.35?±?1.40)?·?10?5 is found which is the lowest value for ultrathin films published so far. The FMR linewidth in this case is 3.49?±?0.10?Oe at 9.6?GHz. Our results not only present a method of depositing thin film YIG of unprecedented quality but also open up new options for the fabrication of thin film complex oxides or even other crystalline materials.