The fact that a manifold´s extremal Kahler cone is open (LeBtrun-Simanca) leads to the possibility of studying extremal metrics from the point of view of a compactness completeness problem in Riemannian geometry. The di_culty is that, without Ricci curvature bounds, the Riemannian collapsing behavior is ostensibly uncontrollable and consequently the nature of limiting objects is almost impossible to study except in special cases. I will discuss some new results in dimension 4 that, independently of Ricci curvature constraints, put constraints on the nature of the collapsing behavior. As in the Cheeger-Tian (2005) result for 4-dimensional Einstein manifolds, if a sequence of extremal Kahler metrics collapses, \most" of the collapsing must occur along Nstructures, and both collapsed and noncollapsed singularities must be point-like. 1