  We show that there is an one-to-one correspondence between resolutions
(equivariant w.r.t. a Lie groupoid action) of a singular subset of a manifold,
and substacks (of a certain type) of the differential stack associated to the
Lie groupoid in question. In particular, we show how to build an equivariant
resolution out of Lie subgroupoids (of a certain type).
