When the composition of a material contains different elements, compositional tomography is required for revealing the 3D distribution of the different elements. The following figure is a 3D result of the compositional tomography by performing a tilt series of EDS mapping images on Ag nanoparticles coated with Pt, where the Pt shells and the Ag cores are shown in semi-transparent green and red, respectively. The Pt shells contain holes with sizes from tens of nanometers to several, which expose partially the cores. This sample was produced by the group of Professor Yi Ding in CEM and Tianjin Key Laboratory of Advanced Functional Porous Materials. The tomography result was obtained by the CEM members and Dr. Carlsson of FEI, and it was published on the cover of the November/December supplement of Microscopy and Analysis.