This data set is comprised of 2048 synthetic scanning electron microscope (SEM) images of powder materials and descriptions of the corresponding 3D structures that they represent [2]. There are 256 images/structures from each of eight closely related particle size distributions (PSDs), as described in Table 1. Fig. 1 shows the PSDs sampled to create the images, and Fig. 2 shows example images from each PSD. Fig. 3 shows a text snippet from a 3D structure file, as well as a rendering of an example 3D powder structure that would be synthetically imaged to generate a 2D micrograph.