In the neutron-rich Ne, Na, and Mg (proton number Z=10 to 12) isotopes
around neutron number N=20, a region known as the Island of Inversion,
the standard independent particle model shell filling is disturbed by neutron
intruder configurations caused by a reduced N=20 shell gap. These intruder configurations give rise to increased collectivity and deformation.
Although the boundaries of the Island of Inversion were predicted more
than twenty years ago, only the advent of the New Generation rare
isotope facility RIBF enabled the experimental quest for the southern and eastern borderlines. My presentation will focus on recent in-beam gamma-ray spectroscopy results on the very neutron-rich fluorine and magnesium isotopes and discuss their deformation and association to the Island of Inversion. In particular, experimental evidence towards an extension to the
fluorine isotopes (Z=9) will be presented. The results indicate an N=20
shell quenching even for the unbound Z=8 nucleus 28O.
