For many applications, micro- and nanostructured materials show a strong correlation between their geometry and their function. We report here the interfacial precipitation of a copper/alkylamine complex to form Cu(OH)(2) nanofibers in a two-phase system (H2O/CH2Cl2). Their aggregation results in porous microbeads. This mesoscale aggregation is due to the formation of a water-in-oil (W/O) emulsion. The fibers formed at the H2O/CH2Cl2 interface adsorb on the water droplet surface leading to spherical networks of Cu(OH)(2) fibers. Our preparation technique is rapid (less than 1 h) and benefits from the simplicity and the tunability of emulsions. To our knowledge, this is the first demonstration of the in situ synthesis of 1D nanostructures that self-assemble at both the surface and the inside of emulsion droplets. We report the successful control over the chemical nature of the synthesized material, its size, and morphology at both the mesoscale (completely hollow versus porous) and the nanoscale (nanoribbons versus nanofibers) by the addition of a short chain alcohol. The transformation of these materials into porous CuO spheres has several potential applications, including a demonstrated sensitive response to visible light (measured photocurrent/dark current ratio of 2.22).