Self assembly of inner drops inside another drop is tricky.  Here is an emulsion where the inner drops self-assemble based on their size.  The larger red drop is surrounded by smaller blue drops.  If these inner drops were loaded with drugs, sequential release of one drug and then a second drug is possible.  This is important in tissue engineering where different releases of different growth hormones are necessary to grow new tissue. This emulsion was generated with glass microfluidic devices. (Photo credit: L. L. A. Adams)