Galaxy Build-up and Evolution at z>=7: Results from ultra-deep WFC3/IR
observations over the HUDF, GOODS, and CANDELS fields

The new WFC3/IR camera aboard HST enables us to survey the sky in the
near-IR 40x more efficiently than ever before -- allowing for enormous
progress in both the search and characterization of very high-redshift
galaxies.  Already in the first two years of observations, we have
deep and ultra-deep observation over >200 arcmin**2 in legacy fields
like the HUDF and GOODS and now CANDELS.  With these data, we have
been able to select large number of very high-redshift galaxy
candidates -- over 150 galaxies at z>=7 including one possible z~10
galaxy -- and study their properties in substantial detail.  These new
selections have allowed us to quantify the evolution of the UV LF and
faint-end slope from z~10, significantly constrain the stellar
populations and dust properties of z~5-8 galaxies, and construct a
general picture of how galaxies build up early in the universe and how
it may have been reionized.  In this presentation, I provide a summary
of our current results and the picture which is emerging.