  We discuss two sorts of generalization of Lie groupoids. One is Lie
$n$-groupoids defined as simplicial manifolds with trivial $\pi_{k\geq n+1}$.
The other is the stacky Lie groupoid $\cG\rra M$ with $\cG$ a differentiable
stack. We build 1-1 correspondence between Lie 2-groupoids and stacky Lie
groupoids up to a certain Morita equivalence. Equivalences of these higher
groupoids are described.
