Essay: The NANO initiative, sponsored by the European Science Federation (ESF), is a five-year program concerned with the vapor-phase synthesis and processing of nanoparticle materials. Arising from an ESF Exploratory Workshop held in 1993, the program, which began in 1995, aims to build bridges between the aerosol community and the materials science community. The activities included in the program, e.g., conferences and various forms of support, are outlined and the themes of the various working groups are detailed.