This column is devoted to partitions of point-sets into convex subsets with interior-disjoint convex hulls. We review some partitioning problems and corresponding algorithms. At the end we list some open problems. For simplicity, in most cases we remain at the lowest possible interesting level, that is, in the plane.

We developed a method, named GraFix, that considerably improves sample quality for structure determination by singleparticle electron cryomicroscopy (cryo-EM). GraFix uses a glycerol gradient centrifugation step in which the complexes are centrifuged into an increasing concentration of a chemical fixation reagent to prevent aggregation and to stabilize individual macromolecules. The method can ...