NanoFabric is a Fortran90 program developed for the geometrical construction of free or supported crystalline nanoclusters. Many degrees of freedom are provided to control the structure, shape, microstructure and orientation of the particle. The substrate may be crystalline or amorphous, and a physically based amorphous carbon is provided. The output files can be used in electron microscopy image simulation programs. The NanoFabric program is free, open source. Small improvements of the program can be done upon request (new structures, new output format, fixing bugs etc…). If you find it useful for you, please acknowledge the use of this program in your publications. Of course, the program comes with no warranty. It is absolutely necessary that you check with your favorite visualization tool that the generated object is correct.