  We have performed a comprehensive study of the Orion Nebula Cluster (ONC)
combining the photometric data obtained by the two \textit{HST} Treasury
programs that targeted this region. To consistently analyze the rich dataset
obtained in a wide variety of filters, we adopted a Bayesian approach to fit
the Spectral Energy Distribution of the sources, deriving mass, age,
extinction, distance, and accretion for each source in the region. The three
dimensional study of mass distribution for bona-fide cluster members shows that
mass segregation in the ONC extends to sub-solar masses, while the age
distribution strongly supports the idea that star formation in the ONC is best
described by a major episode of star formation that happened $\sim 1$ Myr ago.
For masses $\gtrsim 0.1$ \Msun, our derived empirical initial mass function
(IMF) is in good agreement with a Chabrier system IMF. Both the accretion
luminosity (\Lacc) and mass accretion rates (\dMacc) are best described by
broken power-law relations. This suggests that for the majority of young
circumstellar disks in this cluster the excess emission may be dominated by
X-ray-driven photoevaporation by the central star rather than external
photoevaporation. If this is the case, the slopes of the power-law relations
may be largely determined by the initial conditions set at the onset of the
star formation process, which may be quite similar between regions that
eventually form clusters of different sizes.
