  HST ACS and NICMOS data are now of sufficient depth and areal coverage to
place strong constraints on the formation and evolution of galaxies during the
first 1-2 Gyrs of the universe. Of particular interest are galaxies at z~6
since they represent the earliest epoch accessible by current high-efficiency
optical instrumentation. To this end, we have constructed a sample of 506 z~6
objects from all the deepest wide-area HST data (UDF, UDF-Parallel, and GOODS
fields). They have been used to construct an optimal determination of the
rest-frame continuum UV LF at z~6. Our LF extends to over 3 magnitudes below
L*, fainter than has been done at z~3. Over the interval z~6 to z~3, we find
strong evidence for evolution in the UV LF. Though constraints on the faint-end
slope remain modest (and are consistent with no-evolution), the characteristic
luminosity appears to have approximately doubled over the interval z~6 to z~3,
consistent with hierarchical expectations. Remarkably, this shift to lower
luminosities extends to even higher redshifts. Using all deep J+H NICMOS
observations (800 orbits in total), we have been able to demonstrate that the
bright end of the LF (>0.3L*) is at least 5 times lower at z~10 than at z~4,
with a similar deficit being established from our recent detections and first
statistical sample of z~7-8 galaxies using our UDF NICMOS data. In these
proceedings, we discuss what is known about the UV LF and UV luminosity density
at z~6-10 from current data and its evolution relative to z~3. We also describe
several exciting prospects for advance in this area over the next year.
