[en] PLGA nano-half-shells were prepared by the oil-in-water emulsion solvent evaporation method. It is suggested that the structure results from the sequential events including fast solidification, phase separation and water escape. Since these nano-half-shells are nanostructures with low densities, they may have the possibility of being used as carriers for pulmonary drug delivery system. Nano- and microparticles composed of degradable polymers have been used for drug and gene delivery system. Recently, polymeric hollow microspheres were developed for pulmonary delivery of drugs and genes. In general, an oil-in-water (o/w) emulsion solvent evaporation method has been used for the preparation of poly(D,L-lactide-co-glycolic acid) (PLGA) nano- and microparticles which had spherical shapes, although hollow microspheres can be prepared by other methods such as water-in-oil-in-water (w/o/w) double emulsion solvent evaporation and jet spraying with a nozzle. In this article, we report that nano-half-shells could be prepared by the same oil-in-water emulsion solvent evaporation method by adding Pluronic F127 (poloxamer) to the organic phase. Generally, half-shells are not thought to be produced spontaneously, due to their high surface tension. Thus, poloxamer seems to play a key role in generating the thermodynamically unfavorable structure of nano-half-shells