  Let $(M^3, g)$ be an asymptotically flat 3-manifold with positive ADM mass.
In this paper, we show that each leaf of the canonical foliation is the unique
isoperimetric surface for the volume it encloses. Our proof is based on the
"fill-in" argument and sharp isoperimetric inequality on asymptotically flat
3-manifold with nonnegative scalar curvature.
