Colloid-electrospinning is a technique widely used to immobilize nanoparticles in nanofibers. Such hierarchical structures are advantageous because they benefit from the properties of both nanoparticles and nanofibers. Controlling the aggregation state of nanoparticles in nanofibers is essential for the properties of the resulting materials. We investigate here the relationship between the aggregation state of nanoparticles in dispersion before spinning and in electrospun nanofibers. The aggregation state of nanoparticles in nanofibers was found to depend on the aggregation state of the nanoparticles in dispersion. (C) 2017 Elsevier Ltd. All rights reserved.