Combustion synthesis has led to many advances in materials science, in part via the synthesis of powders consisting of particles of nanometer dimensions. Particle morphology is a key concern regarding the powders produced, but also of comparable importance is particle composition. Electron energy loss spectroscopy (EELS) and energy-filtering imaging (EFI) can be used to interrogate the gas-phase combustion synthesis environment for elemental particle composition information. Once established, this diagnostic approach can be used to address control of particle composition and other issues associated with particle formation and growth in flames. The evolution of the particle morphology in a laboratory scale combustion synthesis facility can be examined by passing TEM grids directly through the combustion synthesis flame at various heights above the burner surface, as shown in Fig. la. For the current work, SiOx particle samples are obtained from a SilL/^/FL/Ar flame using a rapid probe insertion technique.