Growth of nanocrystals precipitated in glasses with specific compositions can be effectively limited by diffusion barriers forming around crystallites. For the first time, we do experimentally prove this concept of self-limited growth on the nanoscale for a SiO2/Al2O 3/Na2O/K2O/BaF2 glass in which BaF2 nanocrystals are formed. As shown by advanced analytical transmission electron microscopy techniques, the growth of these BaF2 crystals, having great potential for photonic applications, is inherently limited by the formation of a ca. 1 nm wide SiO2 shell. © 2009 American Chemical Society.