Resent results concerning epitaxial Fe 04(001) films grown by reactive deposition on MgO(001) substrates as well as obtained by oxidation of epitaxial Fe(001) films are reviewed. Conversion electron Mossbauer spectroscopy (CEMS) performed in and ex situ was used to check the stoichiometry and electronic properties with monolayer resolution. Size effects were reflected in reduction of the Verwey temperature for the film thickness less than 50 nm. With further decrease in thickness, the films showed strong deviation from the bulk properties due to formation of a magnesium rich phase near the MgO/Fe3O4 interface. Surface oxidation to gamma-Fe2O3, which can be reversed by annealing, was found using CEMS. The atomic scale surface characterization was accomplished for the first time in situ by the scanning tunneling microscopy, which revealed details of the surface reconstruction and termination.