The cover presents a novel method for synthesizing microspheres with tunable refractive index by controlled assembly of multicomponent nanoparticles. The backdrop comprises highly monodisperse water-in-oil emulsion droplets in which nanoparticles such as silica, titania, and gold are encapsulated and dispersed finely. Subsequently, as water is removed from the emulsion droplets by evaporation, the encapsulated nanoparticles spontaneously assemble into microspheres of all equal size, as schematically illustrated on the cover. In their Communication on p. 3268, Seung-Man Yang and co-workers create composite microspheres by using colloidal mixture suspensions of different materials. This is technologically important because the functional properties such as refractive index can be tuned by changing the components and their mixing ratio.