  Understanding the dynamical transition from capillary-driven to pure inertial
focusing is important to revealing the mechanism underlying the most singular
micro-jetting produced from drop-impact craters. Herein we study dimple
dynamics from the collapse of these craters when the drop is of a different
immiscible liquid than the pool. The parameter space is considerably more
complex than for identical liquids, revealing intricate compound-dimple shapes.
In contrast to the universal capillary-inertial drop pinch-off regime, where
the neck radius scales as $R\sim t^{2/3}$, a purely inertial collapse of the
air-dimple portrays $R \sim t^{1/2}$ and is sensitive to initial and boundary
conditions. Capillary waves can therefore mold the dimple into different
collapse shapes. We observe a clear cross-over in the nature of the dynamics
from capillary-inertial to purely inertial immediately before the pinch-off.
Notably, for singular jetting the cross-over time occurs much earlier,
irrespective of the Weber number.
