We show that for any extreme curve in a 3-manifold M, there exist a canonical mean convex hull containing all least area disks spanning the curve. Similar result is true for asymptotic case in H 3 such that for any asymptotic curvethere is a canonical mean convex hull containing all minimal planes spanning . Applying this to quasi-Fuchsian manifolds, we show that for any quasi-Fuchsian manifold, there exist a canonical mean convex core capturing all essential minimal surfaces. On the other hand, we also show that for a generic C 3 -smooth curve in the boundary of C 3 -smooth mean convex domain in R 3 , there exist a unique least area disk spanning the curve.