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DOI: 10.1002/mame.201700505 by dispersion, suspension emulsion, or miniemulsion polymerization, while the preparation of polymer nanocarriers made from preformed polymers usually occurs by coacervation methods such as salting out,[13] emulsification–diffusion,[14] nanoprecipitation, and supercritical fluid technology.[15,16] Among those different preparation techniques, miniemulsion is particularly attractive due to its ability to prepare nanocarriers from either mono mer or polymer while allowing for the efficient loading of large doses of therapeutic agents, which can be lipophilic and/or hydrophilic compounds.[17] Furthermore, miniemulsion provides the opportunity to finely tune particle size distribution while preparing emulsion with high solid content of polymers.[18–20] The crosslinking of polymer-containing nanodroplets formed by miniemulsion is a particularly attractive method to produce nanocarriers (Figure 1). Hollow nanocapsules can be prepared by a polyaddition or polycondensation reaction occurring at the droplets interface.[21] In order to prepare nanocarriers, the polymer is dissolved in a good solvent and emulsified with an immiscible nonsolvent forming the continuous phase. After the emulsification, a crosslinking agent, soluble in the continuous phase, is added to the emulsion and the poly addition or polycondensation reaction between the polymer and crosslinking agent occurs at the surface of the droplet. When the reaction kinetic is fast enough, a shell insoluble in both phases can be formed at the interface.[22] To control the size and size distribution of the nanocapsules prepared by the polyaddition/polycondensation reaction at the droplet interface, it is critical to control the preparation of the miniemulsion used as a precursor. The two main factors leading to the broadening of the size distribution of the nanodroplets during miniemulsion are (i) Ostwald ripening and (ii) coalescence of the droplets occurring through collision. The coalescence could be controlled by the addition of an appropriate surfactant, which provides electrostatic or steric stabilization thus preventing droplet coalescence. Ostwald ripening is affected by multiple factors such as droplet size, Laplace pressure, polydispersity, and solubility of the dispersed phase in the continuous phase. In general, Ostwald ripening could be limited by the addition of compounds increasing the osmotic pressure in the system. These chemicals need to be highly insoluble in the continuous phase but completely soluble in the Nanocapsules