The goal of this work is to investigate the use of thermal annealing of thin metallic layers buried in a capping ceramic material to obtain controlled synthesis of metallic nanocrystals, i.e., to achieve nanocrystal formation with size control and narrow size distribution. SiO2/Pt/SiO2 films were deposited by electron beam evaporation with different Pt layer thickness, 5, 10, and 25 A. After deposition, films were annealed in vacuum at 500, 700 and 900 degrees C for times from 10 to 180 min. High-resolution transmission electron microscopy revealed the presence of Pt nanocrystals, their average size, and size distribution. By tuning the Pt layer thickness and the annealing conditions, it was possible to control the final nanocrystal size with narrow size distribution typically of +/- 1 nm. (c) 2005 American Vacuum Society.