Hello, in order to make a hierarchy: I have a set of vertices that are separated in disjoint sets of increasing size (2^s), called scales: scale 0,1,2... The vertices at scale s are used also at scale s+1and a graph is build at each scale using all the vertices of smaller scales. Therefore I would like to build an adjacency list like structure that can store multiple neighbor lists per vertex: one per scale the vertex belongs to. Has someone had had experience to share with such a problem using the BGL ? - Thanks. Manuel