Researchers have discovered six new Janus dendrimers that self-assemble into uniform onionlike vesicles with predictable dimensions and a controllable number of internal bilayers (Proc. Natl. Acad. Sci. USA 2014, DOI: 10.1073/pnas.1402858111). They envision the vesicles, dubbed dendrimersomes, being used for drug delivery one day: Each layer could be loaded with various types or doses of drugs that get released over time by enzymatic cleavage of bonds in bilayers or other cleavage mechanisms. Janus dendrimers, discovered by Virgil Percec of the University of Pennsylvania and coworkers a few years ago, are molecules that branch out repetitively from a point and, like the Roman god Janus, have two faces. They are amphiphilic—polar on one face and nonpolar on the other (Science 2010, DOI: 10.1126/science.1185547). Percec’s group identified the new Janus dendrimers during a molecular library search. The number of bilayers formed in the dendrimersomes depends on the concentration of the dendrimer starting material used to make them. Multibilayer vesicles made previously by other means required “very complex and time-consuming methods that do not control their size and size distribution in a precise way,” the researchers note, adding that the new approach overcomes those limitations.