  We summarize the main results obtained recently by our group on the
identification and study of very high-z galaxies (z>7) using lensing clusters
as natural gravitational telescopes. A description of our pilot survey with
ISAAC/VLT is presented, aimed at the spectroscopic confirmation of z>7
candidate galaxies photometrically selected from deep near-IR, HST and optical
ground-based imaging. The first results issued from this survey are discussed,
in particular the global photometric properties of our high-z candidates, and
the implications for the global star formation rate at very high-z.
