  The Helioseismic and Magnetic Imager (HMI) has just started producing data
that will help determine what the sources and mechanisms of variability in the
Sun's interior are. The instrument measures the Doppler shift and the
polarization of the Fe I 6173 A line, on the entire solar disk at a
relatively-high cadence, in order to study the oscillations and the evolution
of the full vector magnetic field of the solar Photosphere. After the data are
properly calibrated, they are given to a Milne-Eddington inversion code (VFISV,
Borrero et al. 2010) whose purpose is to infer certain aspects of the physical
conditions in the Sun's Photosphere, such as the full 3-D topology of the
magnetic field and the line-of-sight velocity at the solar surface. We will
briefly describe the characteristics of the inversion code, its advantages and
limitations --both in the context of the model atmosphere and the actual nature
of the data--, and other aspects of its performance on such a remarkable data
load. Also, a cross-comparison with near-simultaneous maps from the
Spectro-Polarimeter (SP) onboard Hinode will be made.
